I see what you're getting at, but I support the MCPON's stated reasons, even if there are other ones.
You misused a term, I believe. The MCPON certainly knows that he was not 'done' in his duties. This is evidenced by his acknowledgement that he was not done and that he still had ideas floating around about things he could influence, and hopes that the next MCPON will be involved with those initiatives.
In general, I see this as an extremely positive example to follow. I suppose it comes from what I believe the most important tenants of leadership are, which have yet to be shaped by any Officer training regime until I report to Naval Science Institute. First and foremost, in my opinion, the quality of subordinate development is the most important leadership quality one can have. MCPON Campa's actions, both his accomplishments in changing the Chief's Mess and his sudden departure, both illustrate that quality.
Substantively, his abdicating the MCPON throne does many things which help many people out to varying degrees. It gives another Master Chief a chance a rare chance at career advancement (in this case Master Chief Rick West, assuming he is not taken down by 'marital impropriety' allegations), his impending retirement opens up a Master Chief billet somewhere, and his example of sprinting from start of the tour to the end is one to be copied ad infinitum.
Now, granted, there is something to be said about him not "finishing" his tour, but in reality, at his level, you do have a greater deal of freedom in choosing your fate. 'Rank has its privileges' in action, I suppose.