I used to believe the second part of your post--but I am beginning to learn things may have beem more complex then they first appear.
It is possible they allowed Germany to grow in power in the expectation it would stop the spread of communism--perhaps even that Germany and Russia would destroy each other.
Things did not turn our that way--although they almost might have; so maybe the appeasers weren't quite so foolish as they seem in hindsight.
You can certainly make a case for that. I don't think I would go so far, but it's true that Communism was a terrible threat.
In the end, of course, we went in on Stalin's side and helped save the Soviets, so if that was the plan it didn't turn out too well.