No they didn’t, or don’t have to. I haven’t been trained by my boss almost at all, separate people train me on different processes. My boss leads the team, they don’t need to know all the details of everyone’s job and certainly don’t train everyone on everything on what they need to do.

And while the team is their responsibility and what happens in the team immediately reflects on them, that is not the case legally speaking. Internally sure, someone fucks up in the team and maybe the boss gets canned or whatever, but they are not legally responsible of the entire team.

Of course this isn’t true if the person the boss hires isn’t qualified to do the job and were hired because of money, or for instance if that person is way too overworked or are given inadequate tools to their job properly etc.