Lets take a look for it in this way, we all aim high for the peak of our career and what makes us standout is our proficiency and offers we received, while when we go more further, some placed higher bids for us, now as you have said, this is where loyal, integrity and greed comes in, because its not about leaving, but the purpose for leaving and also the timing for it.
I settle for the statement you made that in our career, we aim higher and look for opportunities that makes us gain more recognition and fans, not want everyone wants but in football that's what most players does when they are fully confident in their self and knows what they worth or deserve and since we are not really getting inside information of what team mates pass through, we can not totally know the reason behind some decisions but to generalized it all, no body will leave a club where they are fully satisfied with how everything is going.