I've been through this as well, and it sucks. Sadly, even organizations doing societally important work can be incapable of policing their internal politics and professionalism in even a basic way.

I'm still working on accepting this.

Relatedly, it took me a while to pick up on the fact that "non-profit" does not necessarily equate to "beneficial for society". Many non-profits out there have noble purported goals, but when you actually gain some experience at them you start to realize that they are vanity projects for the wealthy.

[edit]: To clarify, I'm not making the claim that all non-profits are vanity projects, just that there are many out there that are. If you ever do want to work in the non-profit sector, doing some due diligence before applying for a job is a must (I recommend obtaining the publicly reported financial records for a non-profit in Form 990; what a non-profit's founder pays him/herself relative to the average employee speaks volumes about their moral character).

Vanity projects or ways for rich people to defer more money they should be paying as tax to orgs run by / made up of their friends & family.

True, although using non-profits for tax evasion doesn't really work out that well if you die. iirc, HHMI was originally supposed to be a tax evasion vehicle, but started becoming a serious research venture after Howard Hughes expired.