https://www.pcgamer.com/aids-simulator-and-other-games-removed-from-steam-valve-clarifies-trolling-policy/

Just a day after Valve announced a new 'anything goes' policy for Steam—simplistically, as long as a game is not illegal or "trolling," it will be allowed—it has removed AIDS Simulator, ISIS Simulator, Suicide Simulator, Asset Flip Simulator, and Triggering Simulator from the platform.   

The 'games' were all added to Steam prior to the announcement of the new policy (Suicide Simulator and ISIS Simulator were actually added in September 2017, in case there was any doubt that Valve's existing approval systems were useless), and while they could easily fit most definitions of "trolling," they were presumably removed under the old rules: Valve said in the policy announcement that it "won't be making significant changes to what's arriving on Steam until we've finished some of the tools" it's working on to help Steam users filter what they see.