Your manager’s fear of looking bad to his boss reflects his inexperience. (Or a dysfunctional organization, but let’s hope that’s not true.) It’s your skip’s job to provide mentoring to a new manager, and to support him in creating a high-performing team, which includes guiding him through using the company’s performance management process to take care of underperforming employees like your toxic coworker.
Since you have a good relationship with your skip, I think a frank conversation about the effect this person is having on the team will go well. You can also share that you’re worried about it blowing back on you, and your manager’s fear of looking bad. If your skip is smart, he’ll use that opportunity to take a more active hand in mentoring your manager without bringing your name into it.
I also gave the feedback to my manager that I don't think he's handled this well. I brought up that he's, each time, mentioned another excuse for the difficult engineer. He agreed, and apologized to me. He was sincere, and apologized more than once. Meanwhile, I apologized for bringing this up again.
It's discouraging that he didn't have as many other people talking about the guy to him as they have to me. It makes me think I may just have way more problems with him than me, and that I've overestimated how problematic he is; though I also think the other engineers who've complained about him to me are conflict-averse and wouldn't want to raise this to a manager who may pass it on to the difficult engineer. I was also disappointed that my manager said that he doesn't think it's personal, and that that's just how the difficult engineer is to everyone; it's clear to me that that's not the case since I'm living it first-hand.
It was also hard to get to a concrete, specific, actionable behavior change to request the difficult engineer to commit to. It's easy to say "don't condescend to your teammates". It's hard to say what behaviors that entails.
One of the essential but most difficult jobs of a manager is to create psychological safety: the ability for people to raise what’s really on their mind, and to do so with the people who can act on that information.
I think you made the right call here. Telling your manager you were disappointed with their handling took courage, too. Now they can look into it further, starting with talking to the people you named.
Maybe they were just going along with you, “oh yeah, that guy’s a real jerk.” Maybe (and more likely) they didn’t raise it themselves because they’re don’t have the senior mindset you do. If your manager asks them directly, they’ll probably get a reasonably honest answer, although it’ll likely be softened a bit.
> It was also hard to get to a concrete, specific, actionable behavior change to request the difficult engineer to commit to.
Oh yeah, that’s the hell of these things. You end up playing whack-a-mole, too, because HR wants something more concrete than “don’t be an asshole,” and it turns out you can follow the letter of a PIP while finding plenty of other ways to be an asshole.