The Boomers voted for Reagan. They were anti-government because of combo Vietnam/Watergate angst and their parents were mostly New Deal pro-union generation.
Or, less charitably, they grew up and decided they'd got theirs.
do you mean that many would have had jobs, spouses and children by 1984?
Yes, and that this inclined them politically rightwards in a way that revealed the fundamental shallowness of their earlier 'leftism'.
Boomers moderated and moved towards the centre in all Western countries, but it seems to be only in the US that they became more right wing than the average voter.
Could ethnic changes (the Democrats becoming the party of minorities) explain that?
I doubt American boomers were more insincere/shallow in their original leftism than boomers in other countries.
