There was weak pacing too. Look at the early months of the war. The whole "Invasion of Poland" story was over in just four weeks. And then nothing happened for six months! They all just sitting around acting like there isn't even a war going on.
Then suddenly in May, they finally remember they're supposed to be fighting. But do they do it right? No. France, which was supposed to be this big strong power, rolls right over. Yeah right, like that's believable. Any of you guys ever hear about World War I and five years of fighting?
My guess is they saw they were getting low ratings and they figured the war was going to be cancelled. So they threw together all of the stuff they had been saving up for the rest of the war as a grand finale. Then what happens? The war doesn't get cancelled after all! So now they have to rewrite the whole story and make Britain be the new big strong power.
Britain! Like a little island is going to be able to do something when a big country like France couldn't. And they had already written themselves in a corner by writing out the entire British Army. And they had to recast the British government and bring in new characters.