Its really not all that surprising that Marciano ( and many others ) favored Patterson to win. He was after all the reigning heavyweight champion and had accomplished a great deal of things to that point.
Quite a lot of people picked Patterson to win, once you get into it. Obviously they backtracked very quickly after the fight.
Marciano didn't even like Liston. Also, I don't think Marciano took into account that Patterson would be scared to hell of Liston.
A buddy of mine was at Aurora Downs where Liston was training for the fight, watching Liston on the heavy bag. He recalled some clown in front of him trying to impress his girlfriend with his boxing 'knowledge' by saying "Patterson is gonna kill this guy". My buddy said he rolled his eyes as anyone with any knowledge could see what Liston was going to do that night the way he was bending the heavy bag in half. I'll give Patterson full credit for taking him on, however, in spite of Cus D'Amato. It was a no-win situation and he went out like a champion taking the fight to Sonny.
I just read an article which listed Braddock, Walcott, Charles, Marciano, and Johansson as picking Patterson. Ingo definitely did in the pre-fight 1962 Sports Illustrated and Ring Magazine. But why just pick on Marciano? Here are some expert opinions quoted from Ring Magazine's fight preview: Nat Fleischer-----"Liston is rugged but he has never faced and opponent as fast and as shifty as Floyd. Considering the contrasting styles, clouting vs. shiftiness and Liston's performance against Eddie Machen, my vote goes to Patterson." Dan Daniel-----"Patterson will retain the title with a knockout around the tenth." Sam Taub-----"I feel that Floyd Patterson's speed will be too much for Sonny Liston to handle. Floyd moves too fast and punches too fast for the flat-footed challenger. I feel the champion will knock out Liston." Jack Hurley-----"Liston may be bigger and heavier and very impressive looking. But he is too slow, for one thing, and he is flat-footed. The champion will keep the title." Overall, 60% of sportswriters picked Patterson. Of course, they were even more wrong in 1964 with Ali & Liston. *my bottom line is why would anyone consider the opinions of these "boxing experts" definitive or even that important when one looks at their record on fights that actually happened, rather than bowing to their opinion on fantasy fights which never happened or could happen.