One of these days that jacked up lightbulb is going to burn out on stage. Can't do that over and over without consequences.

That was the logic used by those who agreed to support him early on.  They figured people would never support a kook like that, so he could be easily managed.  And even when he became Chancellor, he didn't have majority support and the others who agree to support him figured enough people wouldn't take him seriously.  The Enabling Acts that were passed in 1933, and that gave him the power to become dictator, came when he only had the support of a third of the voters.  But the rest again figured that he could be controlled, so they agreed to give him that power.

And that was it.