I feel its far more likely Google devs are just lazy and don't bother to test in Firefox, much like devs at pretty much every company these days. Unfortunate, but (probably) not part of some deliberate evil plan.
When you have a long-standing pattern of behavior, you need to start using critical thinking, instead.
Is there a benefit to Google from breaking Firefox?
Yes, clearly.
Does Google have the technical competency to avoid breaking Firefox if they want to?
I would say this is very likely.
If you misapply Hanlon's Razor where it's no longer appropriate, you're liable to cut yourself off from the truth.
Now, if YT and Chrome were distaste companies, then we might not have this problem...
Also, as pointed out by others, when again and again these stupidities benefits the bottom line there is good reason to ask if someone somewhere doesn't have a bonus that goes up with every mistake.