Second, You really don't get it, do you? They will not spend money on anything that might actually threaten Google's dominance. They get 30M to play with AI is because they don't get to spend anything on making Firefox a strong alternative for Chrome. If they did, Google will take all their money away and then it's game over for them.
Google does not pay Apple for "access to the user base". Google pays Apple so that Apple does not try to get into the search engine space and compete with Google.
They also pay Mozilla as a way to keep controlled opposition and a (relatively) inexpensive way of avoid threats of lawsuits like the one that MS had in the past. But they don't need to. If Mozilla for any reason decided to stop conforming to this game and went on to actually fight against Google, Google would drop them in a heartbeat. And who would Mozilla go for, Bing? DDG?
> If they did, Google will take all their money away and then it's game over for them.
Because of the position they put themselves in. Also you underestimate how much cash they have.