Simple Larian prioritized making it fun and entertaining, and they were brilliant at marketing those aspects. They also created characters and storylines that people cared about.
Fun and entertainment is rather a broad term. It means different things to different people. Characters, storylines, etc., yes they are important but mostly RPGs audience, mostly.
A lot of people play world of warcraft do not know anything about the lore and characters involved in it.
I learned about bg3 from a channel that makes info about general gaming news.
I am more interested why people who are not normally interested in playing RPGs decided to pick this game.
Marketing and sexy companions.
It's a similar thing how Dragon Age: Origins made waves, Morrigan being sexy (Also apparently Alistair) draws in the general population.
Add a dash of simplicity (DA:O did this via Warrior and Rogue classes being 90% "I auto attack the bad guy") through watered down 5e ruleset and you don't drive off the players who aren't interested in hardcore RPG's.
It is turn-based compared to rtwp.
Personally, that's a benefit for me. I abhor RTWP as it often feels like it just combines all the worst aspects of TB and RT into one awful system.
DAO was far more simpler when it comes to games mechanics then bg3 or any dnd is.
I doubt it matters to general populous if the game has turn-based or rtwp system. You not liking rtwp is your prerogative, same as me not liking turn-based combat.
Something about this game caused to appeal to non-rpg minded gamer. At the start you hinted that the popularity of dao was Morrigan and Allister.
When I look on bg3 companions none of them provoke the same feeling as allister or Morrigan from dao. Maybe I just loved Claudia Black performance in Stargate.
