I'd like to add my voice to the line of though pointing out the decisive French weakness in 1940 as being communications, rather than the sneaky concept of "moral".That "something was very wrong at the top of the French military, and it was not a money thing" is I think partly what was implied by "morale".
Gamelin upon becoming CiC installed his HQ in the Chateaa de Vincennes outside Paris. He didn't think the role of the HQ was such that it needed a telephone line. I.e. in the Battle of France in 1940, the French CiC was impossible to reach by telephone from the outside, and saw no reason why he should communicate out of the HQ by using one either. So yes, despatch riders it was.
The major French problem was pacing and timing. The Germans could run rings around them since the French communications were so sluggish as to make sure that by the time a commander somewhere high up enough had been passed the info and made a plan, by the time the horizon of events had moved on, and whatever he had in mind was obsolete before anyone could get going. (A certain French rationalist, "Cartesian" tendency for how the chain-of-command ought to work also seems to have been unhelpful.) The Germans consciously kept the pace up, and so kept the French on the wrong foot. It clearly worked. The German also fought according to the precept of an OK plan that can be implemented immediately is always better than a better plan that has to wait until tomorrow.
St Éxupery, the novelist/aviator, who flew as a combat pilot in 1940 described things from above (possibly imagery conceived in hindsight but still evocative) as a matter of the German army being this viscous, toxic fluid, seeping in between the units of the French army – and if the French army was seen as a living organism, and its various units as "organs" within that living system, what this German "fluid" was doing was to cut them off from one another, shutting down communication, shutting down coordination, at which point the French army as a living entity started to die. Various "organs" (units) responding differently. Some just shutting down going still, dying, some responding frantically and violently, but overall in a futile fashion, because with the German army "seeping" in, between and through, lack of coordination doomed them. (I've forgotten the original French title, but in Swedish it's called "På spaning mot Arras".)