A lot of companies are moving to full remote for a large portion of their developers. Especially important is that this includes some Bay Area big names. These companies are willing to pay well for talent and don't care where you live.
Toronto, Vancouver, and Montreal have historically paid senior developers poorly compared to what the Bay offered. But we devs chose to be here instead because we like Canada, want to raise our families here. Sometimes because of US Visa issues, but not as common as you'd think.
But now we are being offered the best of both worlds. Better pay than anyone previously offered; you can stay in Canada; you can even work from home every day and avoid commuting.
And it's not like every developer leaving Ubisoft is going to Instacart (though I'll bet a few are). The market on senior developer labor is just suddenly more competitive. Every dev with more than 5 years experience is reevaluating their current total comp and listening to recruiters offering more.
But don't worry, says Ubisoft, we replaced those very senior ICs with a bunch of new people. As long as developers-in is greater than developers-out, I'm sure it will all be fine.