Well, anointing the VP Humphrey as the new candidate, in a process that alienated a lot of the dem's base was a big mistake in retrospect.

I won't pretend to know the history well enough to know if there was any workable approach then, but the convention process in 1968 definitely didn't work to produce a candidate Dems were excited about at the end of it, the turnout was low and Humphrey lost in a landslide.

Also, I think some of it was happening right outside the convention site - Dan Rather was famously manhandled on national television by security guards while trying to interview someone leaving the convention.