Why Did Boxing and Wrestling Evolve Differently?

I'm not nearly the historian of boxing and fighting in general that many fans of the sweet science seem to be. A question I've been trying to find an answer for recently is why boxing continued to be a more-or-less legitimate sporting competition while wresting became, well, the WWE. The simple answer is of course that amateur/Olympic wrestling is boring to watch while boxing can be exciting for the right match-up.

I'm not convinced of that though. First, people have proved to be willing to watch grappling in the context of MMA, and some forms of wrestling are major spectator events (think sumo). From what i've read professional wrestling was considered a legitimate fighting sport until around the 1920s, but was declining in popularity especially after the retirement of the legendary Frank Gotch. The answer to the decline seems to have been the rise of the theatrical style now honed to perfection in modern pro wrestling.

Even with the profusion of fight sport on TV these days it's hard to imagine a new professional wrestling organization that tries to have "real" matches, even if they incorporate judo and jiu jitsu techniques. Although some have argued that the popularity of MMA has increased peoples' awareness of pure boxing, I haven't seen evidence yet that this translates to more viewers for live and pay-per-view events.