Failing wasn't likely, and it certainly wasn't overwhelmingly likely. Unexpected onsides kicks are recovered over half the time from what I've read.
You are too results-driven when analyzing coaching decisions. You should be bashing Harbaugh for going for it onn 4th and 1 this week, but aren't because it worked. But the decision there was a poor one. Coaches can't make decisions with hindsight, they have to go with what makes sense and what might work. The onsides kick made sense because it's basically a coin flip where if it's heads you get a possession with great field position and if its tails, you give the Steelers 35 free yards in starting their possession. Given the way the defense had been playing, where it seemed they were frequently giving up big swatches of yards but not breaking once their backs were against the end zone, it makes even more sense in favor of trying it.
I'm not saying it was a clear and obvious choice to make. Just that the rationale for doing so is certainly there. It can't reasonably be called a stupid decision, at least not if you are using anything other than hindsight.
The 4th and 1 this week was horrible too. Harbaugh's ego and stubbornness are major flaws. He has no feel for the game and situations when making these decisions. It's not about the pure statistics of a situation.
ANybody who thinks we were better than 30-35% to score on that goalline play last week is fooling themselves. And it would be one thing if it looked like it was going to be necessary to get the extra 4 points there but that's where feel and game situation comes into play. The feel of the game should have told you that 3 points was ok there.
This week, the feel was we were gaining momentum. Kick the ball through the endzone and make them go the length of the field again. Your offense had just put together a drive. Your defense had gotten some rest and was ready for the stretch run. Instead you essentially put them in FG territory. If the WR comes down with that grab in the endzone you essentially just handed Pitt the game by making them go 40 yards. Just not smart. You try that shit at home, or when you feel desperate. It shows me panic. Maybe someone remembers another one, but that's the first time I remember Harbaugh trying an onsides kick in his coaching career other than an end of game, desperation situation.