Has Fidel Castro been the most skilled political speaker of the 20th century ?
Certainly not. I would say Castro was a good speaker but not The Best. As an obvious choice I would vote Adolf Hitler to be the best speaker of the last century. He could make people believe in what ever he said. I surely don't think the citizen of Germany, the land of free thinkers like Goethe and land which reverberated with magnificent melodies of Bach and Beethoven, would have been conscienceless not to object to gross injustict he did in the name of Germany. But he could convince them that he was right! There were other powerful orators.. Vladimir Lenin!, who could convince the god-fearing orthodox Russian population that there is nothing more powerful than the power of sickle and hammer and whose influence on the world would eventually paint half the Northern hemisphere red. Then there is Winston Churchill. I would say Castro might be ranked third or fourth.
Why did western democracies appease hitler?
They didn't. Some of us declared war on him in 1939. It was another country which didn't get involved until the Japanese declared war on them and sunk their ships.