Larian was created when WotC didn't own D&D yet. What I've understood from the Larian folks is that they've been D&D fans for a long while, but they never had the money/size for a D&D license/game. Until after the success of their Divinity Original Sin game (and WotC/Hasbro went a little more relaxed on licensing)...
Before their Divinity games they actually made a game they 'sold' to Atari and then Atari left the PC games scene. They made some other games, even something that was called "The Lady, the Mage and the Knight", worked with another studio to make it a DSA game (The Dark Eye RPG). That project went belly up though.
Swen even indicates that his first ever RPG was Ultima VI. For the first Divinity game they looked at Diablo and BG, but "Ultima VII was the base line". But in a 2000 interview, about Divine Divinity, not once did they mention D&D.
They created their own IP because that was the cheapest way to use an IP...
Larian is
great, but they aren't the second coming, and BG3 hasn't been 28 years in the making...
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