This is a situation of their own making. They're the ones that pushed for invisible automatic extension upgrades.
Firefox's old system of you needing to manually initiate upgrades was much more secure, and encouraged user responsibility for the code running on their machines. Google wants to infantilize the user, take away all choice, claim users can't make good decisions and then claim anything control they remove is for the user's benefit.
They're a bunch of stinking liers.
At this point anyone claiming to be a platform needs to regulated just like we regulate platforms before the internet.
I have a friend who works in the compliance department of one of the big international commodity exchanges. They are responsible for regulating the platform (his words) and preventing anything untoward happening, but that also means the company itself cannot "double deal" it can't participate in the markets in anyway. In addition they have two fed watchdogs that do regular invasive audits to ensure that they're actually following the laws and regulations.
It's time for internet companies to be put to the same standard:
If you call yourself a platform get ready to be treated as such.
If you don't wanna be a platform and you have 70%+ of the market get ready to get broken up.