The federal corporate tax can be up to 35%, which is the highest in the world outside of some literally banana republics.

Delaware has a corporate tax rate of 8.7%, California has 8.84.

So yes no one is incorporating in Delaware becuase of taxes, WA, TX, NV and a few others have zero corporate tax.

Delaware doesn't have unusually friendly for business courts. It mostly just has a lot of established case law. It's cheaper for businesses when they know where the lines are on most laws because of previous cases and rulings. Ambiguity is more expensive than the level of bias in most legal situations.