I don't think so. I don't think FPTP really had anything to do with the Nazi's rise to power. FPTP is worthy of criticism but not everything bad in this world is FPTP's fault, and Nazism is an evil of which FPTP is innocent.

You could argue that the specific form of proportional representation being used – the list system – was a factor. Countries which use the list system (such as Belgium, Italy and Israel) tend to be more likely to have unstable multiparty systems than countries using milder forms of proportional representation such as instant run-off or single-transferrable vote.

After WW2, West Germany moved away from the pure list system to the current hybrid system in which voters vote both for an individual candidate and a list. That change was inspired by the lessons of the early 1930s.

The shape of the electoral system was possibly a contributing factor to the Nazi's rise to power, but it was only one factor among many. Many other countries had (and still have) the same system and yet they didn't end up with someone like Hitler in charge.