Many people advised me wait to get tenure before doing work on controversial topics. Why didn't I listen to them?

There are tens of thousands of tenured professors in America. I am not aware of a single example of someone who kept his controversial interests secret for 15 years and then revealed them after getting a promotion. (There are cases where professors developed unpopular views after getting tenure, but that's not what I'm talking about.) In practice, "wait for tenure" means "give it up," for at least two reasons.

First, there's no such thing as "pretending" to be a conformist for 15 years. (Realistically, that's how long it takes to climb the ranks to tenured professor, not including 4 years of college.) After 20,000 working hours of posing as a conformist, that's what you'll be. When you finally get the holy grail of tenure, you'll have a dozen reasons why it's still not the right time to go public with your controversial views (assuming you still have any). Last year I shared the story of a retired conservative academic who was so old (>90) he could barely walk. He told me that "one of these days" he may give up his emeritus status so he can "take the gloves off" and "say what I really think." That's the end result of waiting for tenure.

Second, you can't hide your personality for decades. If you're really a heretic, you'll let it slip at some point, and the ruse will have been for nothing.

Howard Zinn was the author of A People's History of the United States, which sold more than two million copies and played a major role in radicalizing American education. In 1967, the political science department at Boston University voted to award him tenure. However, its recommendation had to be approved by the trustees, who were scheduled to meet for the annual Founders Day banquet. Zinn then accepted some students' invitation to speak at an anti-war rally, not knowing that the purpose of the rally was to protest Secretary of State Dean Rusk...who had been invited to speak at the Founders Day banquet! But he did not pull out. On the same day the trustees were voting on his tenure case, Zinn gave a 45-minute speech railing against their honored guest, the government, and America's founders. He went home assuming he would be fired. Unbeknownst to him, the trustees had already voted to approve his tenure before the banquet.

If you try to make a rational calculation, it will almost always be impossible to justify going against the herd. But in the end, it's people like Howard Zinn who have influence.