Why? FOSS is, at least initially, a charitable project. You work on a database for months then give it in its entirety away for free to all your potential customers and even your competitors with better established sales teams (e.g. Amazon).

They are explicitly not a charity. Isn’t it okay to be a for profit company that sells software with a closed copyrighted source?

Red Hat isn't a charity either. They make a nice profit, and all their stuff is FOSS.

Red Hat makes a Linux distribution. It was not their choice whether to be charitable or not, they are the recipients of the initial charity of the Linux founders and are bound by contract to continuing making their code open as a price for building on open code.

If Red Hat could change the license, would they? Maybe. (Not now but you can’t say the leadership won’t make that decision during financial crisis).

But there's more to a Linux distribution than just the kernel, and a lot of the other pieces aren't copyleft, so Red Hat can change the license, but they choose to keep them open source anyway.

No, it's a collaborative project initially. You work on a tool for months with other developers that each have their own employer, but all benefit from the sum of the work.

That there's freeloaders that benefit from the work without having to expend labour is a side-effect, not the primary motivation.