As someone who has used Firefox since 1.0 (~20 years ago), I fully support returning Mozilla's sole focus to its users. Huge amounts of 'free' money has a tendency to de-focus organizations.
I use and love Firefox, but Mozilla screwed up badly in their funding model and now it's to late to fix it.
Mozilla should have take a large chunk of their yearly income and put it in an endowment, as Wikipedia does. Yes, yes I know Wikipedia bad, rich bastards begging for money, but they have a point. You can't expect money donations and income levels to remain stable forever, you need to plan for the future. Mozilla could easily have had a billion dollars in the bank and if invested semi-wisely that could have generated a steady continual income for decades to come.
Mozilla apparently made no good long term plan for how they'd deal with search engines cutting their funding. They tried becoming a services company, but they are not a company (I mean they are on paper, but they are an open source project more than anything).
You're right money was plentiful and without people to sensibly guide them they lost focus.
Mozilla has been trying to come up with a profitable business model for years. VPNs, privacy masking services, their own mobile OS, feed readers, you name it. Nobody is interested, new attempts at making money turn into cost centers, and the next attempt is burdened by the early shutdown of previous attempts.
Every time they try something, the open source crowd cries out in pain because money isn't going towards their three preferred bugs instead, and the mainstream doesn't care about anything Mozilla does.
They have made stupid decisions to be sure, and the money squandered at the top is definitely infuriating, but no amount of incentives or donations is going to replace the money Google is handing Mozilla to get out of the antitrust laws.
With the reduced funding, Mozilla can fire the overpaid/underperforming executives; and re-hire the tech-focused people who were actually developing the browser.