It does, generally on islands: https://en.wikipedia.org/wiki/Island_gigantism

Humans tend to exterminate them.

And also in environments with high oxygen concentration. At one point dragonflies were the size of cats (the cause is different from deep sea gigantism).

I think that’s an over generalization. The La Brea tarpit types were extinguished due to climate change. It’s also postulated mammoths and such were also affected by climate change, food availability and hunting. None the less, before humans came on the scene large animals came and went.

Of course if they had survived to even antiquity, yes, we’d probably have hunted them to extinction.

Well, sure, there are loads that died out before humans showed up. But of those that existed when we showed up, we have exterminated almost all of them.

> Of course if they had survived to even antiquity, yes, we’d probably have hunted them to extinction.

Often it wasn't even hunting. New Zealand's various giant ground parrots weren't THAT delicious. We introduced invasive species which did the extermination for us, in that case (and many/most bird-y cases, at least).

Hard to know how you could state this so confidently, snacked on a kakapo recently?

I'd expect giants to be more vulnerable to changes in the ecosystem. A new species is introduced that creates competition and the giants can't adapt to a new niche.

I imagine deep-sea is an ecosystem that doesn't get disrupted often. Little new introduction of species. Little human intervention.