Why was Newton a theist?

[Anomalocaris]

This may be news to you, but smart people can be theist too. The guy who proposed the big bang theory was as well.

There is not any perfect correlation between intelligence and the desire to undelude oneself for its own sake.  Intelligence is a tool at the command of a person's desires, it can inform a person's desires, but it does not command a person's desires.

Theism in modern society is just as likely a reflection of the low standards against which a person sets his desires, or the lack of critical analysis of his desires, as it is an indication of a lack of intelligence or knowledge to effectively inform his desires.

Theism could also be an indication of cynical opportunism, exploiting the fact that presenting oneself as a fellow theist allows one to better exploit the part of the society that is less resistant to self delusion and are thus more easily deluded by others.  This form of opportunism is clearly effective enough to gain direct personal authority over half of the world's nuclear weapons, to say nothing of sports cars, private jets, and other bling of cheap wealth.