This makes a false assumption - that Amazon would be on top of existing job creation. Cities already have models that assume/hope for a certain amount of job c

This makes a false assumption - that Amazon would be on top of existing job creation. Cities already have models that assume/hope for a certain amount of job creation (and loss), with some of that being provided by new entrants to the area. If existing businesses aren't meeting the model, they go out and find new sources. The jobs and housing numbers are separate (separate orgs, both flowing from the same model). So, consider this more of a mayor being a salesman meeting their annual quota with a single sale. It's risky, but it's not an issue if it happens - they have already planned for success. Now, if they aren't producing housing to meet their plan, that's an entirely different problem.