Are the disbelievers mentioned in the Quran stupid

I'm going to start by saying that I have very strong faith in Islam, however there is something that's been bothering me. In the Quran, it is described that people who witnessed miracles of Allah and the Prophets would still stay ignorant. This just doesn't make any sense to me. How brainless do you have to be in order to see the literal ocean part and then start worshipping a COW right after ???

Like if I saw that I would've forgotten about everything else in the world.. How would anyone go about their lives after witnessing that. Did Allah purposely make these people idiots? Or do I not have all the context? Also there's no way they secretly knew the truth because if they did, how are they fine with disobeying someone who they know has enough power to kill them in an instant..

Same thing applies to Shaitan too I guess.. he literally disobeyed God while standing in front of him 😭

Edit: I do understand the danger of pride and how stubborn it can make a person. I guess I just couldn't believe that it could get so severe that a person would go against something they saw with their own eyes.