Call_me_jorge said: "Why edit something that's a hit?"
The same reason that lots of shows will go back and make cuts and changes once they are open. Tighten the run time, reduce costs, cut something that audiences never really responded to, the list goes on. Many hits have done it, including the original Broadway production of Les Miserables (trimmed to bring the show under 3 hours and reduce overtime costs) and The Lion King (cut the aerial ballet in "Can You Feel the Love Tonight" and "The Morning Report" amongst some other changes).
Here's an article from Variety a few years ago that talks about some shows that underwent changes even after becoming certifiable hits.
http://variety.com/2010/legit/news/broadway-hits-not-averse-to-retooling-1118021067/