IMO there is no excuse for the Reps running so many candidates. I was told by someone in the know that there is no mechanism (State level??) for winnowing out candidates. If the Reps had a single qualified candidate with a focused message, I don't think this would even be in the news.
I bet the official Republican party only had one or two candidates they sponsored, but I bet they have no way to actually prevent any of the others from running if they get the signatures to do so. It appears to be an at-large type election so I guess there is nothing preventing multiple candidates from each party.
If The Republican Party was so organized as to prevent various candidates from running for office, Trump would not have been in the race and Jeb would have lost. I would rather have a mad scramble than that.