They probably should have thought longer about the success of Baldur's Gate 3 before burning their bridge with Larian.
It wasn't their IP that made it succeed, it was the quality of the developer. D&D as a brand is worthless if they just sell it to the highest bidder and don't give a damn about quality.
On the bright side I would much rather see a Divinity Original Sin 3 than a Baldur's Gate 4 from Larian. Now they are free to do their own thing again.
Tbf Divinity: Original Sin 2 did not come anywhere near BG3 levels of popularity. The difference between those can really only be attributed to the value of brand recognition.