You can surely at least understand the mindset there. Basically, when party A is obviously lying, a party B that calls them out appears more trustworthy, and it’s easier to overlook the obvious flaws in party B’s alternative. Here’s the logic, specific to vaccines:
group A claims vaccines are effective against contracting a given disease
group B points to evidence of actual effectiveness, which vastly falls short of what the public thinks
group B proposes an alternative to the vaccine, implying it’s effective and that group A doesn’t want others to know about it
group A attacks group B’s alternative
This creates an us vs them situation, so if you already distrust group A somewhat, it’s easy to side w/ group B, assuming you have no actual knowledge to parse the available information. The same logic works with anything, you just need a little bit of distrust w/ some authority, evidence of false/misleading statements, and a seemingly credible alternative.
The trick is to not lie/be misleading in the first place so you don’t break the trust. Trust takes years to build and a moment to break, so you need a very good reason to break the trust.