They could just make less money and deprioritise non-engineering/engineering-leadership personnel.

In short, they could become a non profit again, with a single mission - build a open source browser with the interests of its users as first priority.

Others are trying that approach, so I guess we'll see if that's enough

It's definitely enough. The problem is that any money attracts people who glom onto it and suggest interesting side avenues of spending for a "good cause" that's nothing to do with the mission of the org.

They dont need to spend millions on other products and politics for start.