There has been 3 changes in manager since Euro 2012. The way it worked then is not necessarily the way it works now.
He's not popular in the Netherlands, there will always be a lot of pressure on the manager to put the other player up top. It's normal for Dutch national managers to give in to this pressure, especially when under pressure themselves, Van Gaal was the exception.
Van Persie explicitly said he would make a decision on his future based solely on the need to be playing regularly. It stands to reason that he didn't receive the assurances he wanted that he would get those games at United.
Both will work against him, if he's playing everything for Fenerbache, then it's only Fenerbache and the Turkish league isn't much. If he stays and isn't always first choice, then he's too old, passed it and only a sub with lack of match rythm. I'm not sure he realizes that himself.
I'm not sure what the alternative argument is here? That Fener offered him so much more money than 250k a week that he left United, despite assurances that he would be first choice here? That doesn't seem realistic to me.
Obviously he didn't get assurances. I think he decided to leave because he'd rather be a big name in a small club than a former big name in a big club. And he needs to play regularly to get in form and keep his touch. That will probably help him for the 2016 euro's concerning is own form and level of his game, but if he thinks it will help him a lot to become first choice up top again, he might overestimate the backbone of the new national manager.