Canada

Fear.

Fear of losing bodily autonomy and control to mandatory vaccines, fear of government overreach (easy boogeyman to paint), but most of all, fear of unknown things they don't understand (microbiology and immunology).

Too bad they will have to relearn the fear of losing their children to a formerly eradicated disease.

Of course, the bastards with a financial incentive to profit from any patsy that falls for it also perpetuate this cycle of fear and loathing.

Some of it is pure misinformation - the very thing they fear, getting weaponized against them. There’s a way to present things to people that sounds very convincing to someone with weak critical thinking and/or without empirical research experience. These people typically will focus on the few pieces that validate their beliefs and throw the rest out as lies/conspiracy/garbage/etc. It gets kind of dangerous when they hit peak Dunning-Kruger and they totally refuse to hear reason, they usually need some kind of major tragedy close to them to question themselves lol…

I guess some of it might be some sense of belonging. There may be a part of it that is purely about validation from peers.

I’ve also had many friends over the years who didn’t get vaccinated as children over religious reasons.