For the most part you have the financial incentives of pharma backwards... it is very easy to make a killing and because very famous being the kind of doctor or scientist willing to go to bat for pseudoscientific ideas. They get invited to podcasts, make their own podcasts, accrue thousands of followers, get paid to write articles for right-wing think tanks, get easy ghost-written book deals.... and after Trump's election, high-profile positions in the government. This is especially true for people who fail at the normal scientist / doctor career path.

I also don't really think there is any money per se in "shilling" for pharma, at least for like, 99% of doctors and scientists. Pretty much all doctors and scientists I know who dedicated a lot of time to communicating on covid-19, including studying ivermectin, running the trials on it that failed, didn't really get any extra money for doing so. Just a lot of hate mail.