In FPTP, not really because voting third party can split the vote between multiple parties meaning that none of them get a relative majority of votes and their common opponent wins instead. The system encourages you to vote for the next closes party that is the most likely to get more votes (strategic voting). It entirely favours a 2 party dynamic
This is a good video explanation that you may have seen before as it is popular
It's a clickbait title. From what I see it basically says that Hitler gave democracies a common enemy to fight against and rally to defend their system