If you are a programmer, you know this. Every problem that you encounter seems like an easy one that can be solved in couple of hours.
But after you start to work on the solution you find out that the problem is not so easy to solve and that it will take a lot longer than you have expected.
This is bit like what Trump has done wit a lot of his promises. E.g. “Nobody knew that healthcare is so complicated.”
The real issue is, that lot of people did knew that healthcare is complicated. Just like with most of the problems that you encounter as a programmer. Many people will tell you that it is not so simple, but you will not believe them.
You should. Do not be a programmer Trump.