Because they want to provide services where e.g. teachers can exchange ideas and learning content they develop, but where should they do it?
They can't say use WhatsApp or Insta, if they want to facilitate that as a general policy or want to support them, they need a service to do so.
And the only proocol coming to their mind that is already quite tested is activityPub to build upon. But I think it would be a huge mistake to do so, because of all the flaws, especially regarding identity that activityPub carries.
