This is going to be hard to explain but I'll try my best. Let me give you an example:
Suppose there is a man who worships idols. He's been worshiping idols his entire life. But one day, for absolutely no reason, he suddenly says "I should not worship idols. There is only one God and Muhammad is His messenger". Why does he say this? No reason at all. He knows absolutely nothing about Islam. He just decides to take that leap of faith and say it. And every time he starts to think "How do I know Islam is the true religion? I have no proof!", he just dismisses it as whispers of shaytan.
Belief has not entered his heart. His heart still believes that idolatry is true. But he just keeps telling himself "These are all whispers of shaytan. Islam is the true religion". He has no reasoning, no basis, no proof. Yet, he just decides to accept Muhammad out of blind faith. He wants to be a muslim simply because he wants to believe that it's the right thing to do. That's all. His heart is still attached to idolatry, but he just ignores them as waswas.
If someone asks the man "Why do you believe Islam is the truth?", the man will reply "It just is. I don't need a reason to believe". If someone asks him "How do you know idolatry is wrong?", he will reply "It just is."
I hope you guys understand what I'm trying to say here. So in conclusion, what he did is that he took a leap of faith and converted all his disbelief to waswas. Is this acceptable in Islam? If he just keeps telling himself that everything he has always believed are waswas (without any actual reasoning), would he be considered a muslim in the eyes of Allah? If he proclaims the shahadah whilst in this state, would his shahadah be valid?
If you don't understand the question properly, please let me know. I'll try to explain again.