Allies did not want to be harsh harsh on Germany because:
a. Allies did not want to repeat the mistakes committed after the Ist World war whereby they imposed harsh terms on Germany, by virtue of Treaty of Versailles which resulted in the rise of Hitler.
b. It was this humiliating treaty of Versailles with Germany which was imposed by the victors on the vanquished and compelled Germany to give away all its territorial claims and it imposed huge economic burden on it. The War guilt clause made Germany responsible for all the damage war had inflicted on the Allied and made it pay for the damage . This made Weimer Republic highly unpopular among the Germans. Germany was financially crippled after the fisrt World War, little could Weimer Republic do to recover its economy.Treaty of Versailles proved to be a national shame and physiologically damaging for the Germans as they were held responsible for the war and were subjected to harsh terms. This treaty had sown the seeds of the second World war.
c. Thus, Allies were cautious enough of not being that harsh on Germans again.