It's not all game devs, it's the social justice ones. They are insecure about what they make and they've never had someone tell them to improve what they're making. They are artists that live in a safe space, where they can make the shittiest art imaginable and everyone will smile and tell them they did a good job. In fact, that's exactly what happened with Revolution 60. Everyone who says anything remotely negative about the game just gets written off as a harasser. Meanwhile you have people telling him that his game is great and all that shit because he's a part of the social justice crowd and you can't say mean things to people in that crowd.
They are insecure because even with people telling them they did a great job, they don't really believe it. Imagine if you were making something and you were only surrounded by people who only told you you were doing a good job, even if they said it half-heartedly and you could tell. Of course you'd be insecure, because you would not get an honest opinion out of any one about what you're making. And then you are surrounded by people telling you your game is great and you're talented. You release your game expecting all these great things people have been telling you about your game to turn into success. And then the game doesn't sell. So you look for the first thing you can to blame beside yourself. You spent all that time making a game everyone said was good, how could it not sell? So you blame gamergate, anyone who says anything bad about your game, anything that makes you question what you believe, etc. How could it be your fault? You developed your game in a safe space with everyone telling you you were doing a fantastic job. It simply must be something besides you, you tell yourself.
It's what happens when you move safe space culture into something that depends on merit. You end up with a ton of mediocre or terrible products made by insecure people who have no faith in what their peers tell them about what they're making.