Is that common for players to quit to switch leagues like that
Yep, common, 'til the EuroLeague starts its playoffs, and some players like Stef just have a month or 3 months contract to replace a player for injury, same way like the WNBA weeks contracts
Just for example, Alina Iagupova, an euro-star for at least 5 years just transferred yesterday from Mersin (TUR) to Zaragoza (SPAIN)
Seems strange in middle of season thank you
I thought she went to Valencia?
You're right that is Valencia where she transferred to (was looking at the standings, so the mistake), and last season she was one of the Fenerbehce players, Mc Bride was the PG on the second team, it could have been a sweep
It is not that unusual. Since most of these teams do not get much money from fans, they rely heavily on "sponsors"/owners/government for funding. Sometimes budgets have to change in the middle of the season and teams will take offers from other teams to buy out a player's contract. If it gets too bad and enough salary payments are not made on time, the player can void the contract and join another team. Teams that do have resources also might buy out a player from a less competitive team later in the season if they have a serious injury or they purposely leave roster spots open to see how the team looks in the early part of the season and react accordingly.