I'm not sure I agree with this.. The only WWII game I played in 2022 (that I recall) is U-Boat, which I gave up on after about 30 minutes due to the high learning curve. I invested much more time playing fighting games like Soul Calibre and DOA, and those aren't even listed.
As for simulation, I wonder how much overlap there is with Space Sim. I feel like Space Sim should be #1, but if Space Sim also counts as Simulation (multiple tags), then my play of Transport Fever 2 and MSFS would tip the scales to Simulation, but only by counting Space Sim twice as Simulation as well. Exploration also overlaps with Space Sim, Open World, and RPG.
Maybe Steam is counting Elite as a WWII game, seeing that ships adopt a WWII flight model, LOL.