As far as BAT goes, that was what they came up with as an alternative to the ads and to help fund the project. Calling it nonsense is a bit of a stretch when we still are able to see threads about the browser on front page of HN every now and then. The browser is clearly still relevant in some way.
What would you propose as a solution to fund such a project?
That's NOT a mistake, but a shady thing to do, loosing trust for a project where you have plenty of alternatives is the most stupidest thing you can do.
What else is in that browser we don't know of?
Not my problem, just like it's not Brave's problem to fund Chromium development. BAT and the infrastructure within Brave Browser to support it provide no benefit to me as a user, so it is reasonable for me to want to remove it.
In all honesty, you don't get paid very much. It's not going to replace your day job. Yet it's a non-zero amount of income for doing something you would normally be doing anyway.