As soon as Trump was elected, many (myself included) knew it would inevitably end with some type of resignation or impeachment.... because Trump would allow it to be no other way.
It's like if you know someone who constantly gets drunk off his a$$ and then gets behind the wheel. You know it's virtually inevitable that the person will end up with a DUI or worse, involved in an accident; unless of course, they change their ways.
Trump consistently made it abundantly clear that not only was he not going to change his ways, he was going to double down.