You can't blame them for wanting to know. It's a major market, and they're getting their asses kicked. If I had to pick one, I'd pick Edge over Chrome, so it's actually an interesting question anyway.
I switched to chrome just to try it out years ago, and then I probably would have switched to edge when it replaced explorer just to try that out, but Microsoft just got so pushy trying to convince me to use it and forcing it as default and little notifications about how it's the best that I just refuse to use it out of spite now.
I think the number one answer is just that for so long people have heard not to use MS's browser and most people have no clue one way or the other so they just follow the herd. (Not insulting them, there is no possible way for anyone to be intimately informed about every single topic and so for things you don't care one way or the other, might as well follow word of mouth)
I think that the problem here is that Edge inject the poll in a web page, served from a site that is not from Microsoft, not that they asked it.
I would maybe understand that they asked when installing Chrome, or if was from a page from Microsoft. What's next ? Ask because I use bank A instead of bank B ?
picking between a turd sandwich and a giant douche, what a decision to make. Firefox all the way, nothing stinky happening in that direction, no need to just pick between the two because it will always be NEITHER