Large endowments causes that unless you have very strict rules around it like the Nobel prize endowment. You can see how every large charity starts to focus on growing larger rather than its mission, Mozilla is a good example of that.
I see a correlation in some orgs, but can you explain the mechanics? I think I’ve also seen cases where the original mission continues to be the primary compass, so maybe the mechanics of the failure mode are what I don’t have a clear picture of yet.