Yap, I don't know why people are surprise for a streamer who is moving casino.
It's most common things, If they get a better sallary/deal they will move on. Basically it's always based contract payment could be long term, weekly or monthly so once they got their weekly/monthly payment and the contract is not a long term contract. They will move on.
If the contract is long term, and they want to move on usually they will need to pay bail out before moving out.
It's sponsored one so the streamer only has a temporary contract for that sponsor like to make a single video, livestream and complete that contract. After that, the streamer is free to move on other casinos for other videos, livestreams.
Sponsored videos are different than if the streamer works for a casino as a brand ambassador with a long contract.
With sponsored short term contract, after finish it, streamer is free to move on. It's only his own responsibility to avoid saying something conflicts between casinos he is advertising for. It's his own respect for brands he works with in the past, now and in future.