That's the issue. A lot of these undoubtedly smart people are going back home and start working for companies developing technologies aimed at dismantling the western civilization as we know it.
So firstly, I'm not in tech anymore so this is just trivially not true for me (I study animals and most of the people I meet are similar fields). Secondly, there's no company where their goal is destroying "western civilization" (though I'm sure they also have a very sketchy "defense" sector). If there is, they are currently being outcompeted by US tech firms anyway.
The most potent and impactful agent "dismantling the western civilization as we know it" is not on foreign soil.
As opposed to the holy and righteous goal of destroying middle-eastern civilization, one that can be only truly pursued by working for U.S. defense contractors.