Another one I've seen quite often is management wants "it", and then they hire someone who can do "it", but the company/product isn't nearly ready for "it". Think hiring a DBA before you have 100 total rows in your database, or hiring someone to write an AI recommendation engine before you have any users at all.

The "it" person sits around feeling uncomfortable and is inevitably asked to work on something they don't really know how to do and doesn't want to learn. They usually leave before the company ever gets to the point where the relationship is useful.