It does feel awfully abrupt, doesn’t it? I generally explain it to myself as that Sellen really did succeed in taking control simply because Rennala was too broken to meaningfully fight back, but she gazed a bit long into the abyss and got graven massed. When the rest of Raya Lucaria saw what happened to her they then collectively said “welp guess we were right to ban that primeval current nonsense, lets just pretend none of this ever happened”

It really could have done with an intermediate stage where Rennala is visibly imprisoned somewhere, Lusat and Azur actually are moved to the academy, and Sellen begins to show signs of turning into something else