One of the reasons that the early Wrestlemanias weren't likely to excite the Herb Kunze types is that the bulk of the shows were a procession of five-minute (if that) quickies. The most obvious reason for the abbreviated match lengths was that the WWF wanted
to get the entire roster (or as close as they could get) on the card, and that necessitated a large number of short matches. However, given how house show-centric the business was back then, might that have been another reason to not have long(ish) matches
on PPV? As in, the mentality was that if you wanted to see some longer matches, you had to buy a ticket for when the WWF came to your town? Can't give people everything they want to see on PPV, lest people get it in their heads to stop coming to the local
That was exactly the mentality for years after the establishment of PPV, until house shows became a money losing side hustle instead of the central point of the business.