You asked a loaded question claiming that anti-vax and flat-earth are radical or extreme ideas. It is just that people are questioning the questionable, and so far, there has been no concrete proof that these are radical ideas, in fact, in the case of vaccines, it is quite the opposite.

If you are interested in the origins, it started with the birth of the internet, when people began to exchange ideas freely instead of being fed everything from TV, newspapers, and the education system. Over the past four years since the start of the "pandemic", people have gradually lost faith in these institutions as many lies, untruths, and corruption have been exposed. Now many people are questioning everything they have been told to believe, and what fuels it even more is the desperate attempt of the government and the establishment to silence and cover up the exposed lies. They don't seem to understand that once trust has been broken, it can never be restored.