…….he proved to be cleaner than they thought possible. Usually you can find something on almost anyone if you want to bring them down, and you have the power. But they came up empty.
But mostly the liberals can’t except it because they live their lives projecting their own behavior onto others (racism, sexism, ignorance, etc), and they just could believe Trump was clean because they know that they themselves are not. This is why they don’t accept what they have found.