Every president hits their peak, the zenith of a large, historic life. The lucky ones hit it after they're done being president (Quincy Adams), the unfortunate hit it before their presidency (Grant), but most of them hit it somewhere right in the middle (Wilson).
Wilson is rare in that you can point at the exact moment his presidency peaked — his "make the world safe for democracy' speech. That speech really killed, globally. And he rode its goodwill through the war, and then everything started falling apart.
Wilson's decision to spend the better part of a year in Paris for the peace process was and is still hotly debated and criticized. It didn't seem to make anybody happy. Americans felt abandoned and Europeans felt condescended to. The delegations from France, Italy, and Great Britain couldn't stomach that America had sacrificed the least in the war and yet were trying to run the peace process. France, in particular, was mad that Wilson wouldn't go on a tour of her devastated lands, to see what the war had done to them. Wilson's response:
"I don't want to see the devastated regions. As a boy, I saw the country through which Sherman marched to the sea. The pathway lay right through my people's properties. I know what happened, and I know the bitterness and hatreds which were engendered. I don't want to get mad over here because I think there ought to be one person at that peace table who isn't mad. I'm afraid if I visited the devastated areas I would get mad, too, and I'm not going to permit myself to do so."
Isn't he something?
He might actually have been going loony mad though. He had history of high blood pressure and migraines, and would go on to have a serious strokes, and some people who have examined his medical history and symptoms in retrospect believe he started having a series of mini-strokes during the peace process. He would at times be absent-minded and paranoid, at other times giddy and childlike, and became obsessed with rearranging furniture. It's possible these are all the effects of an extremely high-pressure situation, but many believe (and biographer Berg seems to have thrown his hat in with this theory) that he was experiencing neurological damage from strokes or early onset dementia.
His increasing inflexible and irascible behavior made the peace process more difficult, but he did get through it. Unfortunately, the downward slide had already begun.