IMO, that won't happen until either Apple gives up their control on browser "engine" choices on iOS or Apple itself becomes irrelevant.

Consider that browser share usage could shift around as device usage shifts around during a pandemic.

I don't disagree, but would you expect such a significant drop in Safari usage?

It’s possible if people are using company-provided devices at home in lieu of their own, and the company is providing Windows devices while theirs were Apple. I don’t know the likelihood of this explanation, though.

I would personally think this is unlikely. Looking at https://gs.statcounter.com/browser-version-market-share we can see that Safari on iPhone probably caused the overall drop.

Now, I can't see people suddenly not using their iPhone because of the pandemic (quite the contrary actually) - perhaps this signifies a slowdown in iPhone sales?