Your history as to how Hitler came to power is wrong!
It’s important to remember the Weimar government was a parliamentary system unlike us an exe3cutive system. Hitler came to power legally by being appointed to Chancellor (Prime Minister) by the then Reich President Paul Von Hindenburg! The Nazi party formed a coalition with other likeminded parties and affirmed his chancellorship. After then death of Hindenburg (Who was the only one with sufficient popularity to stop him!) and the Reichstag fire he seized total control of government. Even that was legal, the Weimar Constitution allowed such an extraordinary measure if the crisis was bad enough.
No system is immune to Hitlers if the people are sufficiently foolish!