I'm sure the sudden resurgence of C (don't call it a comeback, it was here all along) is because of the sudden Internet of Things craze. I work in embedded systems and there is a lot of interest in "smart" devices right now. All those micro controllers going into those "smart" devices are going to use C, and that's often your only option. So, it's no surprise to me that C is back on top.
I also like to point out that my favorite programming language is (quite often) the one your favorite language is written in