The Tees Valley Mayor doesn't have "seemingly endless pot of money", but he does have a develeopment budget from central govt, part of which he has chosen to spend on the airport as part of his strategy for increasing inward investment - to quote, "inward investment won't arrive at the bus station, it will walk through the terminal doors".
Where that approach differs to Cardiff is that the WG approach seems to be that the airport is being run as a stand-alone business, without this explicit "global connectivity" aim (or have I missed it?)
What is missing in both cases is transparency on what taxpayers money is being used for, and any controls around govt supported businesses competing against private businesses