I think they'll try anything that the manufacturer fleet programs give a good deal on. Then if there are too many problems/complaints, they won't get them again. I've had worse rentals than the couple of Kia Optimas I've driven.

Hertz has had a lot of foreign nameplates in its fleet for some years. There's no real new trend of moving away from American brand cars. It fluctuates, but at times there have been a significant number of Mazdas. For several years there have been plenty of Toyotas. Nissan has been a significant part of the fleet, especially their Inifiniti brand in the premium and Prestige levels. And so on. Kias, Hyundais, these have all been in the fleet for a few years. And most of these are in other rental companies' fleets as well.

I'm actually surprised there isn't a glut of Chryslers in rental fleets, but I'm glad there isn't. Got one recently from Enterprise, though, so they must have taken advantage of some kind of deal.

Don't know if it's still true, but in many cases in the past rental companies didn't actually buy the cars. They would be part of a specific program and were then turned back to the manufacturer (unless they were in such bad shape the manufacturer wouldn't take them back). I'm thinking this is getting to be less the case, but not sure. Enterprise buys theirs. Either way, things like expected resale value come into the equation (which is probably why we don't see a huge glut of Chryslers).