I was curious to know how many people bought the EA, I remembered that it had exceeded Larian's expectations.

Not that Reddit is a good source, but the numbers in the article mentioned there for Steam are close to or above one million.
The number of people who buy into an EA might be indicative of broader reach when the game finally releases, or it might be most of the people who would buy are have, depending on if you think D&D and Baldur's Gate are niche properties or not.