>>95975251
Most Chaos worshippers are regular cultists. They too have the "pray hard and GL" deal going for them. A khornate cultist basically are handed a blunt sword and are told to charge a golden demigod kicking tanks while praying to Khorne.
The Emperor does answer prayers in the form of Sister of Battle saints and miracles, and the Black Templars for example, who prayed so hard one of them gets a cheat code power boost to be the best swordman in the chapter of swordsmen.
Most people on both sides have their prayers unanswered, but the Emperor do grant boons and miracles.
Also its a trope where the Devil exists and is active but God works in mysterious ways. Except the Emperor is much less mysterious.