Britain knew Hitler was building up his navy, so felt that if it made an agreement about how many ships he could have, then at least it could have some kind of control over the growth in order to retain its naval supremacy
The Allies weren't happy, but there wasn't much they could do about this. No one was prepared to do anything about the uniting of the two countries
The Allies were desperate not to get dragged into a war, so Britain and France didn't get involved. Hitler and Mussolini hadn't declared the war, they were just supporting Franco, so it wasn't their fault
Many people thought that they were German people anyway, so why bother to stop it. Plus 99% of people voted in favour of Hitler (who was born in Austria)
Many people felt that Hitler could be a strong ally and a buffer against the Communist USSR and he would need weapons to do this. In addition, the Treaty of Versailles had been unrealistic in its military restrictions, so Germany should be allowed to ignore it
Chamberlain tried to stop Hitler and even met with him. However, he was convinced that Hitler was a reasonable politician and Chamberlain was determined to use the policy of appeasement to stop innocent people dying. He allowed Hitler to take this area because his only alternative was to fight. At least Hitler promised all action would be peaceful
Britain and France now realised that appeasement wasn't working and promised that they would protect Polish independence
Britain and France felt that Hitler was just 'marching into his own back garden' and he should be allowed to defend his borders
Britain and France felt that any alliance that was against the USSR had to be a good thing