It might have something to do with the fact that there were 8 days left in the season yesterday.
It was the last moment you could send your cards to another account and still play them within this season.

Bring your account up as high as possible, get a new starter deck, send the new cards to your old account, and your high level cards to your new account, and get that new account as high in the league as possible.

Just guessing, but I think that's pretty close to the truth about what's going on...