I doubt it is about money at this point since he has been streaming under Roobet affiliate exclusively, so maybe someone can explain what is going on lately.
Its always about money and thats how they make their own living through gambling stream, why would you guys even expect gambling streamer to be loyal to only one site though? They can literally choose whatever sites that suits ( pay ) them the most. Anyway its either the 'other' site ( Stake ) gave him a better deal or probably Roobet stopped hiring him as their exclusive streamer but its probably the former.
Surprising move that I didn't see coming as his deal with Roobet was pretty good and in some old Twitter messages it was stated the deal would go on until 2023. He was hiding the Roobet logo already quite a while but seems like he has stopped gambling completely at Roobet. As you say, Stake probably offered him an even better deal that he couldn't refuse.