LogFAQs > #975250682

From what I can tell it's a mix of a lot of things that have boosted the appeal and popularity.

For one, back when Baldur's Gate 1 and 2 were coming out, the PC gaming crowd was very small. There just wasn't a lot of room for a large adoption rate. Nowadays, PC gaming has grown much, much larger. We're getting most major releases on it (almost everything apart from Nintendo ones) and it's much more accessible to casual people than it used to be.

Second, there were large or wide-scale games in this or similar genres that greatly boosted the popularity in the casual crowd. I think the start of it came with Dragon Age: Origins, and grew a bit larger with Mass Effect, even if that was slightly different. Even people that got into it or were more comfortable with it because of action combat (Mass Effect, Dragon Age: Inquisition) may have wound up enjoying the conversation and story systems, and thirsting for something with more of that.

And third, this is the only game to have come out since those mentioned above that's really gotten a lot of hype and upswell prior to its release. The other, similar games--Pillars of Eternity, Divinity: Original Sin, and the two Pathfinder games--didn't get a lot of marketing or hype before their release. This one had the early adopters already singing its praises and hype for it, combined with almost anyone who played the original Baldur's Gate games back in the day talking about it.

I'd also attribute a small amount of the growth and success to fantasy settings being more popular than they used to be. Lord of the Rings and Game of Thrones were colossal, when other than that people seemed to be more interested in modern or sci-fi stuff prior.