Firefox market share declined first because Google used their market position to advertise ChromeYes, indeed. This may or may not have been wrong of Google, however this is also called "competition". And what did Mozilla do?
It flinched.
Many users loved Firefox, and disliked that Chrome had barely any ability to customize anything when released. It was literally years before you could change even the most basic things about the interface. When released, almost nothing could be configured about it, and it was a far cry from Firefox's ability to give the user what they wanted.
Firefox's response to Chrome's minor speed improvements? Was to literally begin a campaign to become the enemy. Firefox devs worked diligently to make Firefox a second rate clone of Chrome. They removed features, configuration, the ability to modify the interface, and more.
Mozilla could have so easily kept all that configurability, its strong point, its unique factor, but instead panicked. And in doing so it rendered itself incapable of competing on any footing.
Put another way, yes Google had vast resources. Yet this is precisely why you never compete on the same footing as them. You instead compete on what they do not have.
And that was the ability to theme Firefox, to configure it as you wanted, to turn off features you did not want, and more. Chrome had none of this initially. And Google is literally famous for, and incapable of listening to users. They're not built for it. Mozilla was.
And they threw all those strengths away, the only way they could compete with Chrome.
So yes, there were things they could have done. And yes, endless people told them that in bug reports, in emails to them, and more. If anyone's thinking here is myopic (great personal attack, btw), it was Mozilla's.