What caused that to happen?
I am not exactly sure. I felt the same way that you did last month. However, I was assured that it would be Greenlit eventually, whether it took six months or a year (one month was unexpected).
Getting it Greenlit was all on the publisher's side. I know he was putting it into various bundles and on sites like itch.io to get more greenlight exposure. He also got it into a few collections on Steam. Some of the comments look like he passed out a free version of the game somewhere. The commenters who mentioned getting a free game seemed to down vote it, so it must have just been a way to gain more visibility - good or bad.
I had finished the game in December, so it is up to the publisher now for distributing it. I have not had any other publishers for comparison, but Ross (from New Reality Games) seems to be pretty good. I would definitely work with him again.