After Siege of Tobruk was lifted in December 1941 as a result of Operation Crusader , its defences were neglected , many minefields were lifted and detached mines were used to construct Gazala Line and defensive entrenchments and bunkers were not as good as or any deep in June 1942 as they had been in 1941. Besides garrison commander 2nd South African Division commander General Klopper was not an inspired choice to keep up defensive perimeter. Most importantly Churchill intervaned all the way from London instructed Mediterranean Theater commander Auchinleck (who was also not as good as his recent apologists claim to be) to hold Tobruk with a sizable garrison at all costs and Auckinleck despite supposed to know better , couldn't say no so he reinforced and increased the size of total defeat at Gazala Line by reinforcing already doomed perimeter of Tobruk by keeping 2nd South African Division and at least two independent brigades inside Tobruk. Rest is history.
The booty Rommel and Afrikakorps captured in Tobruk was not as big as it was thought. Yes , a sizable amount of supplies fell into Axis hands BUT compared the size of Panzer Army Afrika and overambitious plans of Rommel invading Egypt and Suez with contantly extending rear logistical tail and supplies it would consume (and these plans revised improvised at last minute by Rommel himself whose last triumphs in Gazala and Tobruk along with captured British supplies got over his head) , it was simply not enough. It was just sufficient to put Panzer Army (which itself was tired and suffered extensive losses since Operation Venezzia , attack of Gazala Line) into Egypt and that's it. There was not a steady logistical/supply system properly functioning that would sustain Panzer Army Afrika all the way in the Egypt and keep it there operational even for a brief time , especially considering only Axis held deep harbour-Tripoli-was 3.000 miles west of El Alamein (best British defensive position reinforced by natural barriers like sea at north and Quattara Depression at south , and 8th Army was not as routed as it was thought after Battle of Gazala) and as Panzer Army advanced further to east towards Nile Delta in a naive and very miscalculated move (by overrated Desert Fox himself since he was in favour of marching into Egypt as soon as possible after fall of Tobruk without a logistical sustainence system , at this he was extremely overoptimistic and over ambitious especially receiving Field Marshal baton from Hitler in June 1942 after capture of Tobruk and declared victory prematurely ) they got further and further away from Tripoli their main supply base , not to mention Royal Navy and RAF Desert Air Force became very active in Mediterranean after June 1942 (especially Desert Air Force) against Axis supply columns in desert. Meanwhile 8th Army defeated at Gazala and Tobruk and demoralised , rallied with an extra reorganisation effort just in time in El Alamein defences with help of extra reinforcements from Middle East (9th Australian Division and 5th Indian Division ) and as British retreated towards east , their supply link at their rear towards Alexandria (best deep harbour in the theater , held by British and supply base most developed since before the war ) got shorter and shorter. And with loss of his best intel resource (wireless decryption of US Consultate and military attache Col. Bonard Fellars reports from Cairo to Washington , when US State Dept changed their wireless code , Rommel unable to reach that intelligenge resource anymore ) he advanced blindly into Egypt till bumped headfirst to Alamein defences.
After the war , with effect of both Allied (especially Churchill to cover up his strategic intervention blunders to field commanders during wartime and his pre war politics of starving British Army out of funding with his Ten Year No War Rule as Chancellor of Exchequer ) and Axis propaganda (Nazi propaganda Minister Goebbels created a superstar from Rommel during first half of 1942 especially to divert and distract German public attention from huge Soviet winter offensive in Eastern Front) and revised Cold War realities (when first pro Rommel works were published like Desmond Youngs biography in 1950'ies-which later became a Hollywood movie Rommel being played by James Mason- and memoirs of his Rommel's ex Chief of Staff General Hans Spiedel who became post war NATO Chief of Staff , it was essetial to create good honest German image to convince western public of creating West Germany , its new army and their joining to NATO) , popular historians and entertainers in West created an image of Rommel the Noble Knight German Badass War Genius and superhuman German Afrikakorps myth (no mention of Italians of course who made up more than half of Panzer Army Africa and whose shots killed or wounded their opponents too.) Besides Allies also during and after the war in public image were trying to reflect their war effort bigger in public (after all they werte fighting four German and six Italian divisions till end of 1942 while in Eastern Front Red Army was fighting almost 300 Axis divisions most of them German units with gigantic casualty rate for both sides) by magnifying their opposition in shape of Rommel the Desert genius and his Afrikakorps gentelmen/supermen illusion. Despite his outstanding record as division and corps command , Rommel was no genius , not even a good army commander and he was especially a bad army group or theater commander , he was promoted field marshal too early and too young without necessary staff experience of staff school studies or aware of logistical realities of a constantly functional logistical supply chain. His constant war of movement and mobile warfare tactics with German mission oriented approach operational method (none were invented by Rommel but he made full use of them) dazzling the need of a romantic hero fighting against a desperate odds image , combined with initial batch of lackluster and bad British generals in Desert Campaign in 1941 spring-1942 summer who were still trying to figure out best organisational balance and operational method and in some kind of organisational and operational confusion / flux (British were aping German methods and unit organisational structure too much till 1942 summer which was a bad move since Germans were better in these methods) , created German supersoldiers of Panzer Army and Rommel the Genius legend. However Rommel was strategically and logistically very flawed and made very serious strategic mistakes , overdone/overworked the forces under his command beyond their capacities and eventually , was wiped out in desert campaign by much more professional general (hated and villified Montgomery who was actually aware of his own forces capabilities , limits , strong and weak aspects of his army , what his own troops could do and could not do and knew how to take maximum efficiency from them without overextending/overperforming them to death and by decreasing and compensating battlefield casaulties of his army by firepower and material expenditure and realising importance a chain of constantly functioning supply link better than Germans) in three or four battles between August 1942- March 1943 (Alam el Halfa , Second Battle of Alamein , Battle of El Aghelia and Battle of Medenine)