This is why it is important to keep meeting minutes and do a post mortem in case something goes wrong. Not to lay blame but to be able to figure out how a wrong decision was reached so that similar decisions can be avoided in the future.

Re. whether teams are steady state or not:

I don't think every team can be fixed and I'm pretty sure that a single toxic new hire can potentially derail any successful and well oiled team.

Even so, many teams that do not perform well can usually be salvaged and teams that already work well are best left alone (and should do their own hiring if the org allows it).