As bad as Beckman and Tepper (and Zook) were, the worst 2 coaches in my lifetime were Lovie and Moeller, with Moeller being the worst. By mid-70's standards Blackman was a good coach; he had to deal with ridiculously difficult non-conference schedules and there was no way he was going to beat OSU or UM. With today's schedules he would have gone to bowl games every year, in which case who knows how the program develops?
Moeller inherited a lot of starters from a very competitive team in '77 and it took him all of one year to run the program into the ground. And for those who think Beckman is a jerk, well Moeller made him look like a saint. I was in HS and went to a lot of games during that era - it was brutal.