What factors led to the rise of right wing authoritarian regime in Europe in 1919-1939?

To add to
what was already stated, and an important fact that is almost always overlooked when looking at
20th century Germany is that the United States kept the Weimar Republic afloat during the
1920s.  The US was able to do this because they never actually signed the Treat of Versailles.
By the mid 1920s the nation was well on the way to recovery.  This was one of the major reasons
that Hitler was not able to get a foothold during his Beer Hall Putsch.

However, when our economy crashed along with the stock market, we could no longer send
money over to Germany.  Without the American money, the Weimar quickly crumbled and Hitler was
able to gain his foothold, and the rest, as they say, is history.