The problem is that a lot of people have a very binary view on life. Either something is a complete success or a complete waste of money, rarely do we accept that most projects fall somewhere in the middle.
The binary view is mostly true, unless it's for events or problems they are themselves familiar with. There is a term for this, but can't for the life of me remember it: People think the problems they are dealing with are infinitely more nuanced, complex and unique than the problems other people are dealing with.
And even worse, they don't think probability is a thing. If something happens, it was certain to happen and we just failed to predict it correctly.
So when someone predicts something will happen with a 90% probability, and then the 10% chances happens and the predicted event does not happen, people will talk about what a bad prediction that was and how they were clearly wrong.
It's the same logic that causes people to say vaccines don't work because they don't stop a disease with 100% effectiveness, or that there is no point to wear a seatbelt because people still die while wearing one.