To oppose a president of your own party for the first time in your life and to have so few people in your ideological movement agree with you is an inherently radicalizing experience. Suddenly, the people cheering your words are mostly from the “other side.” It challenges your assumptions.
Some of the anti-Bush conservatives were already pretty radical to start with. #NeverTrump was dominated by people who were respectably mainstream, which in some ways makes the rejection of the grassroots even harder to take. It is therefore easy to start out fancying yourself as being to the right of movement conservatism and end up sounding like bitter ex-conservatives. Reagan-era supply-sider Bruce Bartlett is my favorite example, an erstwhile conservative columnist radicalized by both Bush and Trump. He has gone in short order from Bush being a liberal to Barack Obama being a conservative to calling people whose views he once substantially shared “wankers.”