It's a bit difficult to get to the bottom of why they changed 'Jake from State Farm' from a white guy to a black guy. The original 'Jake' was actually a State Farm employee from Bloomington, Illinois named Jake Stone, who responded to a casting call back in 2011. The commercial took off to such an extent that he acquired his own webpage, "Jake's Place," which in turn led to a Twitter account and unofficial merchandise (t-shirts, mousepads, etc). It's possible that some friction developed between Jake Stone and State Farm over the issue; however it happened, Jake Stone left State Farm and began working seasonally for Normal, Illinois, and also as a bartender for a place called 'Pub II,' where the original 'khakis' hung on the wall, and Jake Stone enjoyed and made the most of his dubious celebrity. As far as I know, though, State Farm has made no official statement as to their dissatisfaction.
Various craziness happened in the meantime. A 2015 online viral rumor started that 'Jake from State Farm' had cheated on his wife, that she'd caught him in flagrante delicto in a bed and shot him. None of that was true, but it did somewhat tarnish the character in terms of advertising.
So, although Jake Stone was coaxed into coming back and reprising the role, State Farm felt they needed a professional actor to fill it. Enter Kevin Mimms (pictured at the OP). In his opening commercial, the original Jake Stone has a cameo in which he is seen to 'hand off' the role to Mimms.
Of course, the alt right/Russian troll crowd has their own ideas about why State Farm changed Jakes, of which I've encountered two variants. The first is the tired old thing about blacks supplanting white people, which requires a certain degree of intrinsic racism from the start in order to see it that way. The second finds a way to work in the Russian anti-trans effort, which claims that the line from the original commercial, "Well, she sounds hideous" was supposedly deemed offensive to trans people, who supposedly run the world and have to have everything their way (so goes the argument) and that's why Jake was supposedly changed - although, it's worth noting, that since both 'Jakes' are male, it doesn't alter anything. If the line were really the issue, they could have simply changed that.
As it is, State Farm has exchanged a somewhat non-photogenic, non-actor for a professional actor who can now be at their beck and call to perform in the role wherever and however they want to take it. And that would seem to be all there is to it.
