Very high cost of living, inflation, uncertainty due to layoffs, salaries down due to a combination of lack of raises and stocks going down, housing price still increasing despite the high interest rates, which have made real estate even more unaffordable. To top things up the green card priority dates for my immigrant class have gone back, so I have even more uncertainty of when I will achieve permanent resident status.
I don't know the circumstances of the people that you describe, but Europe is looking way more attractive than the US. The whole reason why I left Spain was lack of jobs and low salaries, but Covid and remote seem to have incredibly improved the situation (I know from second hand accounts).
The only reason I'm holding on is a combination of sunken cost fallacy and an unjustified optimism in the future. It took me years and tons of effort to move my family to this country, so I'm not ready to give up just yet. I'm also aware than my bad experience is in part due to random circumstances, and if the situation improves (both for me personally, and for the country as a whole) my experience will be different.
Still, I give it a 50%/50% chance that in 3 years I will hate my situation here, give up and move back home.