"It was never really a question," Baldur's Gate III design producer David Walgrave said, according to USG. "We've been doing turn-based for a while now. We're pretty good at it. Dungeons & Dragons is turn-based in itself, so it makes a lot of sense."
In other words, we're doing turn based because we already know turn based, and in our unknowledgeable viewpoint, we think this is how D&D is supposed to be, so we're just going to shoehorn it in.
So, it was a cash-grab move from Larian from the start.
That pretty much sums it up.
Larian never had any intention of making a true Baldur's Gate sequel, they just wanted to make a straight-up D:OS 2 clone right from the very beginning. Larian could have just made D:OS 3, but then they wouldn't have gotten those WotC/D&D and Baldur's Gate nostalgia dollars.
I have supported both of Larian's Kickstarters, I even backed D:OS 1 when it was just at ~20K dollars and did everything I could to support them and spread the word, as they were a struggling studio. I would have never expected them to pull an EA and just completely s**t all over what so many fans love and cherish dearly, simply out of pure greed.
There is much more to life than video games, but it is a hobby that I admire, and such a move is feels like a kick in the gut, and it really hurts.