No—they did not cut costs enough to build a sufficient endowment. Again, income of several billion dollars.

That is plenty for an endowment to build a browser+ in perpetuity... like an order of magnitude in excess. Ladybird/servo are successfully building on perhaps 1% of that?

I'm sure they have some money in the bank and it gets interest, but obviously not enough or handled well enough to avoid the temptation to start an advertising project due to their unsustainable spending rate.

You keep trying to make it sound like they "did everything they could." No, they did not by a long shot.