He knew he was handing the country over to murderers and monsters. It was just not worth the cost to America anymore. And he was right.

He never suggested "Taliban is lesser of two evils" compared to brave Americans attempting to permit freedom for Aghanis and security for America amidst the depravity of militant Islam, while handicapped by pusillanimous politically-correct miltiary leadership (https://www.conservativehq.org/post/how-obama-and-biden-broke-history-s-greatest-military)

The Taliban is exactly who Trump thought they were, and he let them know it:

"We had very strong conversation," Trump told Fox News' "Hannity" of a conversation with Mullah Abdul Ghani Baradar Akhund, a Taliban co-founder. "I told him up front, I said, 'look, before we start, let me just tell you right now that if anything bad happens to Americans or anybody else — or if you ever come over to our land, we will hit you with a force that no country has ever been hit with before, a force so great that you won't even believe it, and your village — and we know where it is, and I named it — will be the first one.'"