I think the main reason the Allies held out in Tobruk is because they had access to supplies and reinforcements via the med because the British had total naval superiority at that point, which is rare for any encircled troops. Also Rommel underestimated the strength of the garrison holding Tobruk, and constantly got thrown back. If he had concentrated his force into one big push rather than several token efforts, Tobruk would've fallen no problem. When it comes to the frictions between British and ANZAC forces I can't see it playing that great a role, and the German/Italian friction would've been even worse, particularly because supplies were short due to British air and naval superiority and the Italian forces were given priority. Pretty much the reason why the Italians lost Africa from what I know is because they were constantly half-starved of supplies from the second battle of El Alemain onwards. Rommel's expeditionary force was in even worse shape due to the Italian priority of supplies.