Well it depends on your goals with the platform. If you want a one stop shop to get all the necessary information in an efficient time then megathreads are great. It's also good at stopping a specific type of content from taking over a forum while still providing an outlet for people to discuss.
If your goal is to idly consume content, then a megathread probably sucks. Same if you want to be an influencer, it'll cut down on your exposure. Megathreads also can hide major developments that can hide behind a thread that people should be notified about. And if there wasn't much content on a platform to begin with... A megathread can force a ghost town.
There are definitely both good and bad things about Megathreads and there's a ton of depth and nuance that could be had.
In this case, I'm not sure whether a megathread was warranted or not though