Why? It's not like they have a ton of money committed after 2015. There are probably good reasons Greinke won't be a National but I don't think financial flexibility is one of them.
What reasons are you thinking of? All I can see is that he sat down with Nats brass two years ago, discussed a trade with a lucrative extension, liked the FO of the Nats but nixed the trade figuring the Brewers were closer to winning it all. They were, and he also threw out a statement saying that the trade would have probably given up so much that if he went there the Nats would have many holes that would prevent them from competing. He left the door open to return as a FA.
I think the Nats are better equipped all around then the Dodgers or Angels are. Kemp is a beast, but Ethier can't hit lefties, who knows if Crawford can stay healthy, Hanley is Hanley not 2007 Hanley, they have no 3B and A-Gone didn't exactly have a superstar year. Pitching wise they have Kershaw and nothing else in the rotation, bullpen has Jansen and League with not much else. Bench isn't good. Catcher could use an upgrade.
Angels have Trout, Pujols, Trumbo, Morales, Aybar and Kendrick. Can Bourjos reproduce his 2011 numbers? Is the other OF really going to be Vernon Wells? Pitching is thin now with only Weaver and Wilson being notable. Santana is gone and Haren is probably gone too, leaving Jerome Williams as the only other guy. Even if they sign Dempster, does that really put them over the edge? Callaspo is not great at 3B and catchers have always been blah for them. Bench is light as well. Bullpen is probably just alright.
Sorry for the lengthy post but if I was Greinke and the teams bidding on me were the Nats, Dodgers, Angels and Rangers, I would say that the two LA teams would need to go way over whatever the Nats and Rangers would offer in order to sign me. Rangers also have other needs other than pitching which may make spending harder for them.
Case and point, I agree that money shouldn't be the issue. I see the Nats (well duh I'm biased) as being the best destination for Greinke if he wants to go to a definite contender (Nats were the only team to make the "real" playoffs last year).