RousseauX
Donor
Basically, once the Red Guards are in occupied territory and separated from their "beloved" Chairman Mao, they'll start bickering over whether to fight or submit. The whole CR is a case of "The Emperor's New Robes" gone violent, so all it takes is for one person to point out that they've been tricked the whole time and the resistance falls apart.
What are you talking about?
The Red Guards were about rebelling against authority in the name of Maoism, it was ended because Mao realized that they were rebelling against his own government and that can't go on indefinitely. So he met with the leaders and told them to tune it down.
In this case you had a real, foreign power to rebel against that instantly unifies everybody. Nothing rallies the people around a flag more than foreign invaders. There is no possible "submission" ideologically to invading Soviets because OTL they were "submitting" to Mao when they tune down the violence.
An invading "revisionist" power is basically red guard's ideological wet dream.