Roger Goodell needs to be fired now that there's decertification and also lockout. This is just one more in about a dozen other failures or poor decisions on his part. He consistently displays poor judgement and lack of objectivity on a range of issues.
In terms of the lockout, from what I can tell it's the owners who opted out of the current agreement, for more up front money as well as a higher % going to them in the remaining pool (as well as a possible 18 game schedule while keeping 4 pre-season games). The players wanted the current deal to continue, and never asked for more money.
When it comes to millionnaires against billionnaires, the owners were betting on the players caving in, needing money, since most of them only play in the NFL for 3 years and end up bankrupt shortly after. The players called their bluff and it looks like legally they are going to win. In the end, if they miss games the NFL is going to be harmed (maybe irreparably) for the next decade, and they completely killed a Golden Goose when it didn't have to be this way.
If you're going to talk about greed, look no further than the owners negotiating a $4B scam deal where they steal from TV stations even if a season doesn't happen, and where they are still charging season ticket holders full price for a season that may not happen or will happen with replacement players.