The fact Corbyn ended up being voted leader by such a massive majority in the first place, despite only being put on the ballot as some kind of token alternative, suggests there is very much a problem with the MPs.
When MPs...i.e. members of a democratic party, decide to go about deliberately undermining and ignoring the result of a democratic vote from their members, then there is VERY DEFINITELY a problem with the MPs. A very serious problem. It's not 80% of them who fall into this category. It's 80% who have lost faith in Corbyn's ability to sort this out, which isn't an unreasonable view to take at this point even if you like or want to support him...I don't reallly have faith in Corbyn's ability to sort this out, but I certainly don't see how it's his fault. If it was his fault he'd never have been elected in the first place.
What exactly is the pplan of this lot who've been deiberately undermining their own party for months? None of them have offered any political direction themselves. None of them offer a plan. They have just thrown their toys out of the pram because their members told them in no uncertain terms that they were a bit shit. Corbyn is merely the result of that.