Why theists believe in an illusory God is because they are compelled by 'zombie parasites*' in their brain. * not real parasites but a sort of neural set of connectivity driven by an existential crisis.
Before theists go further in taking a big leap of faith, theists should pause and realize there is a real person 'the empirical-you' making all the above claims.
Philosophically theists need to invoke Socrates' 'Know Thyself.'
Know thyself meant theists need to understand why their empirical-you is trying to mess the person's well being with all these sorts of thoughts [ending with an illusory God] which cannot be proven.
The above meant theists need to understand what is going inside their head[brain], mind and body, that drove theists to a desperation to conjure the idea of an illusory God out of nothing.
I don't think theists had even bothered to 'know thyself' and what is going on inside their brain.
If theists have not understood the mechanisms that drive your thoughts and actions, how can theists be so confident their conclusion 'God exists as real' is reliable, especially the unproven illusory God.
My thesis on why theists jumped to the illusory idea of God is because theists are compelled by "zombie parasites" in their brain that control their thinking and pyschological state.
The analogy is the equivalence of zombie ants
Watch this Video:These Brain Worms Turn Ants Into Death-Seeking Zombies
Look inside the head of a doomed ant overtaken by a mind-controlling parasite.
Inside the ant, the worms turn deadly. Ants usually get multiple worms at once, and most stay inside the ant’s abdomen.
One worm, however, will takeover an ant’s brain, commanding it to essential seek death. At dusk, ants usually return to their nests.
But the infected zombie ants climb blades of grass and other vegetation, holding on to a plant by its jaws until it gets eaten.
Once it gets eaten, the parasite can then lay eggs in its new mammal host, and begin its dark cycle anew.
https://www.popularmechanics.com/scienc ... g-zombies/
Parasitic Mind Control - National Geographic
Thus when theists understand there are 'zombie parasites' that compel theists to conjure the idea of God to soothe an existential crisis, theists will disinfect and get rid of these parasites to promote a greater sense of well-being.
Note, Buddhism [& others] is doing just that.
[btw, I am not a Buddhist per se].