My suspicion of Trump meant that I was naturally suspicious of many of his cabinet choices (Rick Perry not exactly nuclear energy material, Ben Carson hand-picked to dismantle HUD, etc.), but...
We have to acknowledge that late in a Presidential term, you have had some turnover because--with the election close--you're not going to get the major policy changes where a competent person really matters anyway.
That said, working for Trump is a natural selection process. People who are principled and competent don't want any part of it. Within my own discipline--Economics--he hasn't hired any of the traditional conservative economists like Marty Feldstein or Greg Mankiw, and he fired Janet Yellen without any good reason.
But... if we just look at the National Security Advisor position, Bolton isn’t a late-first-term firing. Going sequentially, he chose to replace Rice on his Election Day (not terribly unusual, but a lack of continuance none-the-less). Trump’s first pick was Flynn (now a convicted criminal), then acting Kellogg, who Trump decided NOT to make permanent, then McMaster, (left voluntarily), then Bolton (resigned in protest) putting Kupperman briefly in charge before being replaced by O’Brien. Six appointed or acting in 3.5 years.
That’s astounding. Also notable (and mentioned by Travis) is that - unlike all predecessors- the acting person in charge stepped down before a new one could be appointed. Before Trump, most National Security Advisors stuck around for and entire term and then some (e.g. Lake, Berger, Rice, Hadley). Obama had 3 (in eight years) ‘W’ had 2 (eight years), Bush Sr 1. Clinton 2. Carter 1, Ford 2, Nixon 1, LBJ and Kennedy shared 2. Only Reagan had an equal number, and that was over a full eight years, and each had an orderly replacement.
...and that’s just the NSA position. There’s half a dozen other cabinet-level positions that have similar turnover and turmoil.