"and resigned under pressure of a cooked-up "ethical" probe"
That's not exactly how I remember it.
There was a lot of nasty talk about him committing adultery then divorcing his first wife when she was in the hospital dying of cancer, or something like that. But we were giving him the benefit of the doubt on that gossip, and he was hanging strong.
Then it came out that he really did commit adultery in his second marriage, then dumped his second wife to marry his accomplice, and that's what sank him. His undenied faithlessness lost him the support of the faithful.
There was also an ethical probe into a history class he taught. It ended up going nowhere but was a big part of his decision to resign.
Newt has too much baggage, to put it succinctly.