How does this affect any company outside of the other two rivals not being able to play catch up?
Arc, Brave, Edge, Vivaldi or any other Chromium-based project can't really make a difference on the web yet, big thanks to the Chromium codebase; changing mostly visual bits, adding some cryptoish features, built-in adblocker, more hooks to system for usage analysis, etc. Even still, too many things going to the Google's services, maybe because of addons or phishing protection.
I don't know if it's some kind of "if it works, don't fix it" and/or "don't reinvent the wheel" thinking but that's for sure web and users pays the price not the companies.
I think similar things for Android, Firefox, Windows and Linux. They're dominating their positions and holding their territories at all hazards and sometimes this defence means destruction of alternatives, without regard to qualifications and qualities.
This is a bad thing for me.