i still don’t understand why they were against the ussr and now against most aes countries (especially the prc), gives me red flags (pun unintended)

It always seemed to me to be leftover red purge sentiment, brought to you by your friendly occupier. Stalin was pretty critical of theparty at the time as being somewhat toothless in the face of thousands upon thousands of members being arrested/losing their job. The backlash against the militant wing was pretty severe, so I think that is why they ran so hard in the opposite direction.

I have no good answer for why they suddenly issued their anti-China statements. They probably thought it would help win them seats? I actually have a lot of friends who are members that are much more pro-China than the party's official statements would lead one to believe.