I wish Kaku said God is the best theory if he was discussing science. Since he didn't say that, then people will "think" he was being religious. With the Christians, we have the Bible theory, creation science and its scientists. Secular science believed in this before the 1850s. Today, God, the supernatural (Genesis) and the Bible has been systematically eliminated from science.
All the various, unknown authors of the bibles, re-telling of tales and fables that were passed down over and over, as much as two hundred years after the alleged events, it rivals Homers'
illiad, in its fantastical content.
When you look at the very deepest foundation of the entire doctrine, when you go to the theological reason the various books were written, you are left with this conclusion the texts tell us over and over:
Ignorance is bliss
Reality has all the earmarks of a naturally caused and functioning universe. We have no solid evidence of any gods or any supernatural realms, this despite multiple millennia of theories and claims and suppositions and books and icons and so on. Not one single verifiable shred of evidence that any gods exists (and even an argument that states that if there were proof, it would defeat his requirement for pure faith), and in fact, a very youthful science that shows more and more every day that a god isn't even needed for reality to exist... god theories crumble quickly under the light of scientific knowledge.