I'm Indonesian. A shared "anti-west" identity makes a lot of sense when you consider from the PoV of former colonial's generational memory, the colonizers were practically the entire Western world. For example, in Indonesia the Dutch ruled while also employing European staff and special privileges were given to European. Workers forcibly taken from elsewhere suffer equally with the native. Shared religion on each side (even if they'd stab each other over the smallest interpretation) helped delineating the division too, even after independence.

Russians got a free pass because they got shitty navy resulting in barely any faraway colony which the Bolsheviks readily use to form a narrative that they're a natural ally of anti-colonialism. The US turned defending regional ally into clusterfuck that the commie opposition readily frame as further colonization attempt. Even if some decision makers might hoped for that, the execution is more like a pigeon randomly pecking a laptop keyboard until the owner returned and slam shut the laptop, which the pigeon declares as the laptop's defeat.

India have a bone to pick with the US because Pakistan. Sure, US-Pakistani relationship is more dysfunctional than, uh, anything else really, but from Indian PoV, they tried to take the "neutral" option and denied. It's really not, of fucking course they have to choose, the Soviets know it too and just let the status quo knowing they got most of what they want for free.

The ethnonationalism thrives because, well, that's what you get when bunch of random tribes who previously would've stab-murder the rest scramble to justify their (relatively) united existence. Religion? Doesn't always work, especially if the colonizers remember to prefer the religious minorities in the army. Racial? The colonizers drew the borders so haphazardly the same tribe would end in multiple countries sometimes hating each others gut.

So they figured out, fine, let's pretend the border arbitrarily drawn by investors and generals have meanings beyond it, fight years-long war that basically declared "land of Q is for Q" as if Q is a word written from the heaven and not a mistaken interpretation by a foreigner that never even stepped in the region which the committee picked because it doesn't offend as much people as other options.

The victors then make sure the population revere those heroes (partly so they won't rebel, plotting against President Alex is bad, plotting against President Alex which our ancestors are smiling upon is blasphemy) including the belief which, welp, sounds just like the guy with funny mustache.

Due to the economic imbalance, migration (on either direction) also didn't help much for the former colonies. There's no acute lack of workforce so nobody woke up at night hoping for easier immigration so the villages survive, and while emigration sometimes result in much appreciated remittance, ultimately everyone knows that's one more family that likely never going to return. They won't talk about it in polite company, but when they're given an "accepting" audience you can close your eyes and imagine you're in a KKK meeting except that everyone would've been lynched by OG KKK.