Going into the RF field myself, I've been troubled with the license costs of tools like HFSS and CST. After a brief test of the open source tool OpenEMS I've landed firmly on the newer open source tool EMerge (https://github.com/FennisRobert/EMerge). It's a little rough around the edges still as it was released in the fall. But I've already gotten good results from it designing my own RF hardware.
Apart from that I wonder how much of the resurgence can be traced back to more active conflicts around the world? There is a booming Drone and EW development within the military sector which could be what drives it?