Meng Lei hadn't planned on establishing a god system initially. He had only come up with the idea after he obtained the 48 existential planes.
To him, his main means of gaining strength was still the system. Power of faith was ultimately just supplementary.
After all, the worst thing here was that Meng Lei still hadn't lit up his divine fire even as of now. Well, that was awkward!
What was divine fire?
Divine fire was a tool that turned power of faith into power of divinity—in other words, it was a power of divinity converter. If power of divinity were electricity, then divine fire would be the power plant!
Even if Meng Lei had vast amounts of power of faith, he wouldn't be able to convert them into power of divinity anyway without a divine fire.
In other words, even if Meng Lei had 1,000 existential planes acting as his power of faith domains, the vast amounts of power of faith they produced would only pile up and accumulate.