2 days ago, AoE4’s Steam store page seems to have removed the game purchase option by accident.
It had been restored within a couple hours. However, at the same time, AoE4 was also removed from the Anniversary Collection bundle. As of this post, it hasn’t been restored, despite still being listed there.
https://store.steampowered.com/bundle/28326/Age_of_Empires_25th_Anniversary_Collection/
Expected result: restore AoE4 to the bundle