I think halvings-driving-fomo is a myth. Each halving is possibly a catalyst for the crowds-waiting-to-jump-in, but not the reason for them occuring in the first place. Even without halvings, there would be speculative bubbles, then they'd pop, and the bubble attracted attention and people would start forming a line, but not buying until price begins to confidently move upwards.

Since there's little actual utility in using bitcoin right away (even if it was accepted everywhere, but you have fiat, why would you need to buy btc and immediately sell it?), people who'd like to invest would never rush buying until price stabilizes and begins growing. This naturally produces these "steps": BTC goes up 5-10x, then mania kicks in, then it goes 2-3x higher and then pops 2-3x down. Every convinced investor bought before the mania phase, weak hands sold off at a moderate return or at a loss, while a bunch of new people got interested.

Halvings are just one of those points that help tipping off the balance for the already formed crowd.