It's the other way around, Mozilla Corporation is profitable and those profits go directly to the Mozilla Foundation which owns 100% of it.

This idea that Mozilla doesn't have enough money to fund Firefox is just wrong, Firefox development is perfectly sustainable, it earns more money than it spends. If you want to give money to the Mozilla Corporation instead of the foundation, you do the same thing as with any company: you purchase products from them (such as their VPN or MDN Plus, both of which are owned by the corporation).

> Why is the browser arm organized as a for-profit at all?

So that they can make business deals with the likes of Google, which they wouldn't be able to do as a non-profit.

Edit: I really wish there was a single thread about Mozilla here that doesn't devolve into this being like 80% of the comments. Maybe one day.