Well I think that’s because Discord is an easy-to-use and popular platform that makes it easy to form communities and manage them.
Discord has many users and should thus be an easy platform to onboard people on. It allows you to gather your community in one location to make announcements, provide updates, and have direct conversations with your customers.
Not only can you communicate to people one-on-one (and vice versa), but you can also talk to other people in feeds.
Discord allows you to develop a personal relationship with your like-minded community members instead of blasting links at them. You may host discussions, stream live events, generate new ideas, schedule calls, and promote your campaign. You are free to assist the community in any way you see proper.