We were just told how gods are created -- by people needing/believing in them.
The ghost Sekai in the prime timeline began to emerge around the time Wakana started researching the Girl Who Couldn't Breathe and discussing it with Akira. If more people were doing the same, what is currently an intangible ghost would likely be given form. Sure, they SAY that Sekai never died in this timeline, but that is probably not true. She died, and Ami (and possibly that timeline's Sensei) brought her back as a God.
Now that i thought about it a bit more.
This is even nothing new.
There are a couple of stories out there where gods come to be, or gain their power, from people believing in them.
And the most recent story that came to mind, and i had that thought already but forgot, is the series "American Gods".
There are some parallels with LiL and i wonder if Sel took some inspiration there.
They even also have their own "Techno Gods" in American Gods, like i think it was the "Information Age God" and the "Internet God" and whatnot.
It's like how we have the "Wire God".
And maybe the wire god came to be through Maya, or by Akira how he'd imagine a god that would be associated with Maya's IT comparisons.