Rather than building a product that informs medical professionals about effective interventions, I wonder if the creator would have had more success if he deeply explored what sources of information these medical professionals pay for now - do they pay for anything at all, such as UpToDate, and don't want to pay this because it's an additional expense? If the creator found which sources people are using, the creator could sell this database as a feature for these partners and widely disseminate this data through partner channels rather than creating a competing source of information. It seems to be a case of this being a good instance of a B2B2C model, where selling this service to other businesses that sell directly to medical professionals could be more viable than trying to sell directly to them.
Alternatively, if the creator wanted to sell to patients, rather than medical professionals, the blueprint here is all of the consumer reports companies, such as Wirecutter, which is one of the New York Times's most popular services. Here, again, a "Wirecutter for medical interventions" could be quite successful, and you could sell this service to media companies that provide consumer reports as a service that would bolster these companies.
It's bad the creator wasn't able to find traction, as getting more medical data into the hands of consumers could have a huge postive impact over time.