Its insane and I think its crazy that so many people don't understand why initial buyers are upset.
Because it's the internet and no matter what your opinion is someone will argue with you over it.
That and some people seem to love an excuse to throw the word entitled around.
But really Greenlight is about getting attention and promotion for your game so you want to give it away cheap to get votes, reviews, buzz etc. Early Access for the most part should be about alpha funding so in that case you're already on Steam and don't need promotion but rather funding to finish or continue working on/refining the game etc.
I'm not really sure what they were thinking and I'd be curious to know who approached who. The whole charity argument isn't really cutting it either considering so little by default is going to a true charity.