People didn't find a reason to make the jump. Those who didn't buy the second game didn't want to do it because they weren't caught up, and those who did play the second game didn't want to risk being burnt again.
There's a difference between a direct sequel and a new game when it comes to good word of mouth. Even if the word of mouth did spread, most people wouldn't have played it because they would need to know the story of the first two games. And considering the bad word of mouth that went through with the second game, they didn't want to play that one. Much like the way I have trouble recommending the series because of that game in particular.
I would still argue that episode I and III are over rated in metacritic, just had to jump in with a quick personal opinion.