For one, they simply have had a better product, at least in the past. Part of their large monopoly is due to just being better outright for a large portion of users (presumably). Are we to punish making overly-good products?

For another, sell to whom? And why would they be a good steward?

And yet another, there's literally Chromium, which other browsers (built by other corps) use, e.g. Edge, Brave, etc.

Did Google have to open Chromium? No.

Disclaimer: I hold these opinions weakly and would love to learn more about why they might be ill-premised.