Not much to hate in the Discovery crew, which was pretty much like Kirk's in having essentially no aliens other than the XO. I mean, TPTB could afford to place a couple in the mess hall scenes, but Lorca probably never had to exchange words with those. Also, the enemy of your enemy. Every aspiring usurper probably learns to appreciate alien scum for said scum's potential in ousting the standing Emperor. And then unlearns, in order to rid the next usurper of his or her power base. Timo Saloniemi
as Locutus of Bored said, Saru was aboard Shenzou with Burnham. Lorca was in the business of grooming Burnham, and he might not have been displeased with Saru's record. Lorca is, above all things, a very practical character.
Saru: "Captain, if we can't engage the spore drive and are trapped in deep space, we'll certainly starve before we reach home." Lorca: "You worry too much, Saru. You know the old saying, 'First Officer, Last Meal'." Saru: "Wait. What?" Lorca: "Oh, uh.... Look over there! A Gormagander!" Saru: "Huh? Wait, where'd you go?"
The sheer variety of inferred explanations on offer in this thread (many of them plausible, but not all consistent with one another), says something to me about the approach the writers took to this show. All we really know about the backstory is that Lorca lost his previous ship and crew, and then wound up commanding this ship and this crew. How did it happen? How much of it was incidental or fortuitous, vs. part of a plan? We don't know, and we have no way to know, and I strongly suspect the writers didn't know either. They just figured "it'll be there on screen as a fait accompli, so naturally viewers will take it for granted that he just did it somehow, never mind the details!" (And never mind that those details really make some important differences to how the plots and themes play out.) "And if some of them have questions... well, he'll be off the show soon enough anyway, so those questions will be moot, right?"
Mirror Lorca was in cahoots with Section 31 (Black Badges!). They gave him what he wanted (Discovery and crew) in exchange for defeating the Klingons and advancing multiversal travel. He was probably a prisoner on that ship as much as Burnham.
Nah, I doubt Lorca was in on the Black Badges. Section 31 likely put them there posing as Special Ops or something like that with their actual mission to be on standby should Section 31 give the word or if they saw reason to execute Lorca. By the time the whole Mirror Universe storyline got going, they got tangled up with the CMO in what is colloquially referred to as an Andorian Tonsillectomy and therefore weren't on hand to do their jobs when the moment came.
I have a feeling making the Black Badges Section 31 was a late season decision, considering they just completely disappeared after Episode 3.
I lean more toward a seed planted for further down the road. "Further down the road" just happened to not be Season 1. As the season progresses, there's just no opening I see that you can work Section 31 in.