To be fair, he deserves credit for job he did with 49ers. That was his crowning achievement
3 years before his arrival 7-9, 8-8, 6-10
his 4 years 13-13, 11-4-1, 12-4, 8-8 (became his typical toxic self) --> shown the door
4 years after leaving 5-11, 2-14, 6-10, 4-13
I'm a Niners fan. I can speak (reasonably) intelligently to this.
Harbrau walked into a petty good situation. That was a very talented roster, particularly the OL and on defense, that he inherited. They just suffered from years of poor coaching...Erickson, Nolan then Singletary. Two years before his arrival, they went just 8-8 despite outscoring the opposition by 49 points with 5 Pro-Bowlers.
Harbaugh came in, assembled a very good coaching staff and finally got the team to play to its ability. The first 1.5 years they were your typical smash mouth offense, strong defensive team that would suffocate teams. Then, mid way through year 2, Alex Smith went down and they caught lightning in a bottle with Kaep and the pistol offense that mixed in a lot of RPO to take advantage of Kaep's freakish athleticism. They rode that all the way to the SB. The last drive of that SB is, to me, where things started falling apart. They had a 1st and goal on the (IIRC) 3 yard line with a chance to win. They also had one of the best OLs in the league and one of the best RBs in league history. Seems like a no-brainer, right? Nope. 4 pass plays. They lost.
In 2013 they still ended up with a very good season going 12-4, but cracks were appearing. They reached the NFCCG, but lost to rival Seattle after a lot of questionable second half play calling.
In the off-season leading up to 2014, everyone was already tiring of Harbaughs shit. A few weeks into the season, it was clear the harbrau-49ers partnership was untenable. They tried to turn Kaep (a one-read QB if there ever was one) into a pocket passer. It went poorly and the team imploded over the last two months. Injuries piled up and it was clear the roster didn't want to play for him anymore.
BTW, a majority of that talent that harbrau inherited was courtesy of Scot McGloughan, not Baalke. Baalke had a solid first couple of drafts after taking over, but then tried to get too cute. Their 2012-2014 drafts were large-scale disasters and the major reason for the plunge into the abyss following harbrau's departure.
Harbrau deserves credit for turning around a hugely underachieving team, but it wasn't like he took a bunch of scrubs to great heights, or turned over a lousy roster. I've said before, in the short term, he's very good at whipping talent into shape and getting the most out of them. He's just really lousy at sustainment after a couple of years.