Listened recently to a very interesting interview of Lee McIntyre. He is a Research Fellow at the Center for Philosophy and History of Science at Boston University. He wrote How to talk to a Science Denier: Conversations with flat earthers, climate deniers, and others who defy reason. He goes to 'Flat Earth' conventions and other denier group meetings to try to understand the thought processes of the adherents. (I did laugh when I learned that there are different factions of Flat Earthers, with differing fundamentalist views. One faction considers Australia to be a hoax!)
Turns out that it's an issue of trust. The deniers simply do not trust the sources of any information contrary to their views.
Though I'm not a 'denier' and have been vaxxed for Covid, it is undeniable - pun intended - that there are legions of examples of government 'authorities' spouting bull**** and medical 'studies' that conclude what turns out to be bull****. Trust in the institutions of governments is at an all time low.
Thus, Mr McIntyre's thesis is that the only way to change the beliefs of deniers of anything is NOT to plonk facts in their laps and ask why they are so stupid as to not understand the implications of those facts. Rather, it is to gain their trust - hence the word "conversations" in the name of his book - or gain the trust of people whom the deniers trust, then nudge them with facts that are the most easily demonstrated as being from a trustworthy source. But don't bother wasting your breath citing 'the government' or 'the medical authorities' or 'the scientists' in the abstract.