most casual users gave up computers for smartphones years ago
I would consider either statement to be completely false. While less people have full blown desktops almost everyone has laptop and modern laptops are good enough.
I would agree that there are many poor countries/places where people can only afford smartphone. But hopefully the future of humanity is to get better rather than going down to that level.
Good enough for what? I am not sure I understand what you are claiming or how it disagrees with an OP. The point is, for many users the computer is just where they run a browser.
It does not matter whether they have desktop or laptop, and how powerful they are.
Well there is a big difference between MANY and MOST. There is a whole world of creative people to whom browser on a phone just does not cut it.
Which is the bigger threat?
There's no secret plan here. Priorities have changed since 2002...
My point was that we’re not typical users - most users don’t use a traditional computer outside of work anymore as the phone fills that gap for them.
Microsoft isn’t threatened by Linux because they have way bigger things to focus on these days - ubiquitous mobile devices and proving Windows’ relevance in an age of web browsers everywhere.