And it’s not only GGG which does it either.
Torchlight Infinite also has a breakneck pace, and even if being P2W the actual content they deliver is top-tier mechanically. And it happens reliably every 3 months as well.
Even Grim Dawn with being a SP game and not bound to any timeframes is delivering vastly more in the same timeframe. And they’re a relatively small team of what is thought to be less then 20 people, hence 1/5th of what EHG has.