I know many of my friends who used to work at Meta, Google, Amazon, etc. who have applied for this visa, or Canadian PR to move away from the US. People prefer having the emotional safety of not having to uproot their lives when they lose their job, over a few more bucks.

People at senior levels in big tech are now earning 400k CAD. That should afford a nice life.

For the bulk of H1 holders (who I can assure you will not pick up 400k CAD jobs) it's not necessarily a switch to an easy life with great salaries once CoL is accounted for. I wouldn't want to make move to Vancouver as an example for $average unless I had serious cash for a family home etc - property prices are wild.

The jobs H1 holders will want don't tend to be in the "affordable" parts of Canada either.

The speed at which these Canadian offers were consumed speaks far more to the desperation of many in the US stuck in Green Card wait lines that can take decades depending on your country of birth - all the while being at risk of loss of status should you be unfortunate enough to lose your job in the multi-decade wait. I don't think we are witnessing the flight of the top 10% from FAANG here in many cases at all.