It isn't one particular thing. I think last spring the staff was satisfied with the roster they had going into year 2. And the spring portal wasn't nearly as active as the winter portal as a whole. Also, some were contactually locked into staying for the season unless they wanted to be financially penalized (for lack of a better comparison, think of it as trying to break a year lease 4 months into it). When season 2 ended, the staff picked up where they left off in trying to reshape the roster to how they want it (specifically the OL). But many players that left had their own reasons... a chance for more playing time, a chance for more money, a position change, etc.