All very good points.
I hadn’t considered the aspect of the Allies arming and training local forces, but it must have been a crucial factor.
Combined with the Japanese displacement of the colonial powers and, as you mention, the inability of the colonial powers to reassert their control in the face of flowering local independence movements, the training and weapons must have put teeth into those movements which they lacked before the war.
I expect that there was also a fair amount of weapons scavenging from both sides by locals in the wake of the withdrawal of both sides and the weapons and ordnance left after battles and perhaps in field or even warehouse stores.
There were certainly communist movements in some of the colonial countries, but on closer examination they tended to be strongly nationalist / independence movements informed by communist doctrine relating as much to overthrow of the local rich and powerful as to the colonial powers, rather than purely communist movements existing in a vacuum.
The US missed a great chance to avoid the Vietnam war when Ho Chi Min sought US support for Vietnam’s independence in the 1950s, in the foolish belief that the US as the nation founded on grand principles of independence forged in a war freeing itself from colonial domination would actually be sympathetic to those in other countries pursuing the same aim. His approach to the Americans indicates that, at that stage at least, he was far from committed to some doctrinaire Moscow, or Peking, line communism but that he was primarily interested in gaining independence for Vietnam.