There’s 3 errors here.

1. You’re overestimating how much people watched controversial movies. Yes, people still went, but they still had relatively small audiences.
2. Major studios don’t publish niche movies anymore. There was a time where they put out like 1 maybe 2 major blockbusters a year and then had a 100 small “eh, it’s ok” movies along with a few experimental things. They don’t do that anymore. If it’s not a $100M movie, they’re not interested. This is in no small part because people don’t have the time or attention to give to something that isn’t knock-your-socks-off spectacular.
3. The nature of what we consider “controversial” has changed. 99% of “controversial” movies aren’t an unpopular take on something, they’re either deranged and delusional flights of fancy, OR they’re a perfectly normal take that contradicts someone’s delusional fantasy, and thus gets review bombed.

Nothing happened. You are apparently just not aware of what is controversial lately.

Dogma wasn’t available because it was controversial, but because different people claimed to own the movie.

Controversial releases are still happening. However, costs are higher, ROI is lower, the industry is consolidating, so the safest option wins out.

Pressure campaigns all over the place. A hundred million dollar investment can be derailed if one person or issue gets cancelled.

The US government is currently viewing mergers and acquisitions through an ideological lens.

Controversial doesn’t make as much money.