Regarding "Not having Monty hurt LMAD90 at first", a pull-quote from Adam Nedeff's book from audience warmup guy (and future Nick Arcade host) Phil Moore. He states the obvious, but he was there:
“I was only hired to do the audience-warmup so I was never there for meetings or behind-the-scenes stuff. So if you ask me why Bob didn’t work out as host, I can only talk about it in terms of theory. I think Monty left too much of an imprint on that show in the years he hosted it, to the point that being a great host wasn’t enough. The audience just wasn’t ready to accept ANYBODY other than Monty in that role. Jump ahead to 2008 [sic] when they revive Let’s Make a Deal on CBS, I think that’s ultimately why they went with Wayne Brady, who is a great host.
Now, maybe there’s some guy out there named Steve Wyzanski that nobody’s ever heard of would make a better host than Wayne. Maybe Steve Wyzanski would be the best host that show’s ever seen. But he’d fail because Monty was so successful in that role that Let’s Make a Deal is to a point where you can’t have someone host it who isn’t a name somehow. And I feel bad for Bob if that’s the case, because he couldn’t control that. Today if Bob Hilton came along and wanted to be considered for something, he’d just have to start up a Youtube channel, post videos for a year, get 100,000 subscribers, and the networks would give him more of a shot”
One last note from Adam's book: Monty and co-producer Dick Clark had originally agreed to have Dick host the show, while it was being developed. Monty sent Dick some tapes of the show, and a couple of days after he got them Dick called Monty to turn down the job. Quote, "I can't do the show. I don't know how YOU did it, it's too tough for me." I somehow doubt with all of Dick's other commitments that a longterm set of commutes to Orlando would have worked out, especially as The Challengers got ready to launch, but in development there WAS a plan for a bigger name than Bob Hilton to host.
Maybe Dick would have been enough of a name (I generally think Phil Moore is 100% correct here) to get the audience to give him a chance. My gut instinct says that there is no combination of events where LMAD makes it past Fall 1991 no matter what it does. Truth died that year. Daytime Wheel died it's final death on NBC that year. Clearances for anything besides Days and Another World were in the dumps. They shut down production of Classic Concentration, only to bring back reruns, only to leave reruns going when they pulled the same numbers as first-run shows.
Even if Monty's the sole host, even if Dick Clark (a name) hosts the show - there probably isn't a timeline where LMAD goes past Summer 1991 at least on NBC.