How could one think they know more than the legit scientists when they have not done one single hands on physical learning experiment?

About what?

Remember how wrong Fauci was ? ...

Its not so much I think I know more .. as not trusting others blindly. People with an agenda and/or funded studies tend to find things that align to the goal rather than do pure science. There are a lot of examples over time, Covid failings of parts of the science community are among the most aggregious. So, to me .. some skepticism is more than warranted until enough data and studies have been assessed and reviewed.

I'd say ego. And probably overestimating their "knowledge" which a lack of expertise can lead to, like over compensation. Maybe a need to feel in control.

Not sure, without full context.
Although these legit scientists do keep discovering more that invalidates whatever their theory previously was. So there is that.
There are wisdom beliefs that defy what science believes although science seems to be slowly catching up to some of it.

Pfft i’m more appalled by the people who believe mainstream print and media that isn't verified 🙄 yet is widespread published and republished and believed and touted as facts when they are not.

Anything from covid to evolution to the Israeli war .. bs mass media

I can’t stand such people.

Hubris

Theoretical Science is overrated.
Look how much new information JWST has provided us since Hawking passed.

Depends on who is paying them

The Dunning-Kruger Effect.

The public's faith in science has taken a pretty big shot from all the lying liberal "scientists" pushing an agenda instead of facts. People no longer blindly trust science or the "news" media.

Poisoned by conspiracy theory mind viruses

People like gregloa here is your answer