The advance had stalled to logistic difficulties before any forces were sent to Greece. It was because the advance had halted and it appeared from Ultra intercepts that there would be no Axis offensive action for a number of months (Rommel was telling his High Command how ill equipped his forces were) the decision was made to send troops to Greece in the belief that these troops would have been replaced by fresh troops from the UK before there was a renewal of fighting on this front. Unfortunately for the Allies, while Rommel had been busy telling the HQ in Germany how unfit for battle his units were, he had decided to launch on offensive anyway, which caught the British and Commonwealth forces totally off guard.
The Book definitely says O'Conner wanted to advance and the major reason for no allowing to was the upcoming deployment to Greece, not solely there were logistical issues, and O'Cooner owuld have need significant naval logistical support. But the framework the decision was made in was either Greece or Tripoli, and put to Churchill in those terms. (but there is also teh factor the Generals were firmly gainst Greece, so may have presented it that fashion even if it were not entirely the case)
But the book makes a bit of the withdrawal of the 4th Indian and replacement with Australians causing a delay earlier in the campaign, and given the timeline the book sort of says that the 4th inidan was withdraw and sent to east africa to prevent it's deployment to Greece (but only sort of)