> Would Chrome have gained that much popularity if Google hadn't been the most used search engine, nay, website in the world?

Yes, Chrome was absolutely superior to Firefox in every way at the beginning.

> impossible for new entrants unless they invest billions

All industries require that you invest billions, and it’s to compensate the civilization-long effort of R&D that the other company did. Reasoning-by-absurd: Should Boeing display all the plans of the band new Dreamliner so that it doesn’t take billions for new competitors to emerge? Should all companies make their blueprint public so they can have immediate competition? No, Google invested in browsers and set up new norms in WWW in exchange for their position on the market. The benefit to the general population has been excellent WWW norms, to be honest.

I’m thinking outside the law framework but to me, no corporation should be have 51% market share. But that’s wishful thinking, not the law (also, market share is something economists struggle to define).