Why did the future allies engage in appeasement (WW22)

Their policy of appeasement was a disaster - countries hope to avoid conflict by giving into Hitler's demands. For example. he acquired Austria and a small portion of Czechoslovakia. Countries thought he would be satisfied with that territory and leave the rest of Europe alone. After all, Europe was still recovering from WWI. They did not want to engage in another one! Well, he aggressively took over the rest of Czechoslovakia and invaded Poland. Even after he promised not to. Another world war started - something which they wanted to avoid in the first place.