The unpleasant truth...
Nobody knows what a president is really going to be like until they become president. It's a crap shoot every time. We've had pleasant surprises, and unpleasant ones.
That we have bestowed vast powers on the central government doesn't help.
That candidates often spend a lot of the election cycle pretending to be someone they're not doesn't help.
That the system itself selects for wealth, access to the existing political establishment, and power-lust doesn't help either.