I admit, larian probably threw out the announcement a bit too fast.
Under ideal circumstances waiting may have been better, but then it would not have been included in the Stadia announcement, and there were already rumours of the game's development and a previous leak (though a third hand source, so it didn't gain much traction at the time) that was starting to get more corroboration. I don't know how long it could have been delayed before there would be nothing left to announce.
Yeah, my feeling is that this is why they had to announce it when they did: because it was going to be announced for them. A friend of mine was asking about "is Larian doing a new Baldur's Gate?" before any announcement had been made and the games press were already gearing up to make a noise about it, apparently.
