40k is not a satire of "Jesus," its a satire of Jesus-obsessed materialist Britain. How can you say that 19th century Britain wasn't obsessed with worshipping a dead god? They worshipped Jesus, put him into every part of everyday life, said that if you didnt worship him you'd end up in hell being tortured forever, etc etc...
There doesn't need to be an entire 1:1 translation of the Bible into 40k for it to be a satire. A carrion-God Emperor of (white) Mankind who is "apparently" watching out for all of us, at all times, and gives us manifest destiny to rule all other races? That's the modern political Euro conception of Jesus, ensconced the same way into an Imperial state.
The British Empire was extremely secular? You might want to brush up on your history. The COE (Britain's State religion) was not friendly to other religions inside the Empire. Especially at home. The British Empire was a devout place. You couldn't own property as a non-Anglican Christian until 1846! And they said their Jesus-God was responsible for everything, everywhere, at all times.
Outside of Egypt and Ethiopia, Christianity exists in Africa why exactly? India they found it was too difficult to break their faith, so it wasn't worth the bother when they could extract resources anyways. But Africa is heavily Christian for no reason other than British missions.
Bourgeois & wealth-focused is exactly how the Imperium is set up. They don't care about anything other than control and wealth being sent back to Terra. That's part of the satire too.