Why 85% of AI projects fail

Many companies are willing to throw themselves in the fascinating world of AI and learn from the benefits it brings. Usually the story goes as follows: the directors committee decides that their company should lead the AI innovation ecosystem in their industry. In order to this they hire a team with great skills, spend a vast amount of money on resources and after a few months'PUM' they find themselves at the starting point with less money and no trust at all for AI. What mistakes have these companies made? Is AI just a hype and has no benefit at all?