Ironically this is an indication of how popular Discord has become. Some of their more popular communities are massive which often results in too many people attempting to chat in real time. Forums as we all know allow for a more ordered conversation thus spreading the load on oversubscribed channels. It's worth noting this is not the only addition Discord is currently testing.
We've seen multiple social media platforms adapt in order to expand their user base and this is no different. In my view the majority of forum software has been slow to adapt when it comes to capturing new audiences which makes our job harder. I've seen a lot of forums migrate to Discord in the last few years and I fear this may well attract a few more.