If God left he isn't everywhere and in everything in the first place. If he knows everything then eh, I think that only ties in with being in everything and everywhere. Which is an incomprehensible concept unless it was just the universal essence itself that somehow possessed some sense of consciousness. Think 'The Force'. But that isn't even the type of "God" we speak about .. deities are more humanized, individualized, and flawed despite being supposedly flawless. At least the mythological ones were more honest in this. These humanized versions are humanized for a reason. For humanity to grasp at what simply wouldn't be understood.
An individualized God is what majority seem to think about. What is truly absurd is how this individualized God with all these jam packed flaws spreads this concept of its impressive purity and perfection. A perfection that could not exist so long as this "God" is a part of it = omnipresent. Imperfect world, imperfect being. Wrapped up in imperfection. Like we are.
This is, in part, why Christian theology settled on the concept of Trinity. There were lots of different interpretations of how "the Father" and "the Son" were related, were even different deities, and so on. "Trinity" emphasizes the idea that "Father" and "Son" are metaphorical, and reconciles the typical notion of gods as merely being humans (or at least very similar to humans) with the idea that there is only one God who is all powerful. Of course, critics of Christianity at the time made fun of the idea that a "monotheistic" religion worshiped a "trinity".
That tangentially leads to why Christianity, based on the God of an obscure tribe in a far corner of the world, ended up becoming the predominant religion of the Western world. The idea that God became man and
suffered with us. That God is not some invisible man sitting on a throne in the sky arbitrarily deciding the fates of all mankind (variations of this concept were essential to most deities/religions around this time). That God is not some sort of super-Zeus: if he were, THEN He would be an Asshole for letting people suffer. But no, He came and suffered with us. As per Job, the suffering isn't something to be justified or judged: it's just there, a part of life. As Totenkindly put it,
It rains and shines on the good and bad alike.
Bad things happen, but God is there with us, if we take care to notice. THAT is the reason for the belief in Omnipresence.
There's a meme along these lines:
And if you think about it, it's more than God not being an Asshole, but God showing us by example: this is how He wants us to be for each other.