Market makers buy stock when the price rises — not because they're bullish, but because they have to. That's delta hedging: a mechanical, risk-neutral adjustment of their position.
When retail traders buy call options en masse, market makers become short gamma. That means: as prices rise, they must buy more and more shares to neutralize their delta risk.
This mechanical buying pressure — without fundamental conviction — is the fuel behind many gamma squeezes. Market makers have no choice: they follow the mechanics of their hedging strategy.
The market doesn't just move based on opinions, but also based on compulsion.