It's not that you're wrong, really. Certainly, more lorries could be sent, particularly if there's no war with the Soviet Union.
The problem is the scale of what's required. It's really difficult to improve the logistical situation of an army 1100 miles from its major supply base. It takes a vast number of lorries, because each one has to carry not only its cargo, but its own fuel as well. And it's so far that a round trip would take, in the terrible North African roads, probably almost a week? At that distance, doubling the number of lorries increases the size of the force sustainable at the sharp end by a much smaller amount. And the half life of a lorry in those conditions is so poor that you need a constant flow of replacements just to keep up with attrition, all of which have to pass through. the limited port capacity of Tripoli, while paying Malta's tolls... it's a hell of diminishing returns.
For example, the Germans calculated that supplying a motorised division 300 miles from its supply base with the 350 tonnes per day it required would take 1200 lorries. For multiple divisions three times as far away, we're probably getting into tens of thousands of lorries...