Winston Churchill is actually the man who more than any other person 'saved' Europe. If it wasn't for him Europe would have remained under Nazi or (if the invasion of Russia had still failed) Communist domination to this day, and the 'mighty Albion' would have become a shell of an Empire dominated by whatever dictatorship ruled Europe.
Churchill made a load of mistakes in his life, but in 1940 he got it right
I think that is a good one paragraph summary, Churchill warned of Hilter from the earliest days of Hitlers rise, warning the British Parliament and people what Hitler was. He was treated as a joke basically and branded a war monger.
His defining moment is 1940
You ask, what is our policy? I can say: It is to wage war, by sea, land and air, with all our might and with all the strength that God can give us; to wage war against a monstrous tyranny, never surpassed in the dark, lamentable catalogue of human crime.
What General Weygand called the Battle of France is over. I expect that the Battle of Britain is about to begin. Upon this battle depends the survival of Christian civilization. Upon it depends our own British life, and the long continuity of our institutions and our Empire. The whole fury and might of the enemy must very soon be turned on us. Hitler knows that he will have to break us in this Island or lose the war. If we can stand up to him, all Europe may be free and the life of the world may move forward into broad, sunlit uplands. But if we fail, then the whole world, including the United States, including all that we have known and cared for, will sink into the abyss of a new Dark Age made more sinister, and perhaps more protracted, by the lights of perverted science. Let us therefore brace ourselves to our duties, and so bear ourselves that, if the British Empire and its Commonwealth last for a thousand years, men will still say, "This was their finest hour
."
The highlighted parts in bold, shows exactly how Churchill saw Hiltler and Nazism.
As to Churchill keeping back the Australian Divisions, thats partly true. The British did not want to give up their finest infantry forces in the Middle East. but the 7th Divvy was sent home in Dec1941/Jan 1942
before Singapore fell (how else could so many have been captured in Java??), the 6th at the same time, only the 9th was kept till after El Alamen.