What did Hitler, Mussolini and Hirohito all prey upon when gaining fascist power before World War II

I don't know your options, but here is a list of some of the things that they preyed upon:

-antisemitism and racism, fear of foreigners and of others: Antisemitism and the other related ideas were already present in the society, but they used it to their advantage - they blamed the others

-weak economy - before their rise to power, there was en economic crisis and such crises make people more vulnerable to propaganda