Absolutely. There are many other ways people end up unmotivated, but the most common I've seen has to do with things that are within the realm of their manager

Absolutely. There are many other ways people end up unmotivated, but the most common I've seen has to do with things that are within the realm of their manager - possibly with escalation to someone higher up. I've encountered only five managers who fully exemplify this, but they had an outsize role in keeping good people who others might not have been able to keep, keeping them productive (at least enough of the time to satisfy their work commitments while they dealt with other issues), and attracting more good people (because of word of mouth from the existing good people). It seems the key here was to have the conversations when they were needed. The advice here "Make your job easier and don’t." doesn't correlate with these great managers at all. At least two of them to my knowledge have given reports the advice (and assistance) to find opportunities elsewhere.