Most teams have not yet signed long-term contracts with players, which means rosters can change very quickly.
Most organizations haven't signed contracts with players. It looks like everyone locked in their roster and dispersed to other teams. People have contracts for either a month. Almost everyone will reshuffle in 20 days, except for the top-tier organizations. The roster could be completely different in a couple of months or even 10 days if the team fails to qualify for an event. It's not particularly interesting. Sometimes changes are exactly what a team needs. Even if it initially seems like losing someone is a step back, it can actually be a push towards progress.