If you get more conservative as you age, you didn't internalize a new way of thinking. There are old communists that I'm sure are less "mentally flexible" which means they'll tend to look at things through a certain (communist) lens. If you get old and "go conservative", you've just ran out of extra processing space for pretending.

Longer term exposure to US propaganda does in fact work.

Older people are more likely to have accumulated wealth/property by virtue of having had more time to do so, and are more likely to want to defend it (and the status quo that gave it to them) politically.

As time is going on however, each successive generation has less and less, and with it less investment in maintaining and defending the way things are.

tl;dr: mind economizes more as it ages?

That being said, there's gotta be a stake of material conditions and environment that people have, which influences their ideological view...

This isn't an iron law it just describes 1 or 2 generations that were bought off by higher pay, housing as a cheap investment + guaranteed retirement, and frothing-at-the-mouth nationalism.