One) because they weren’t ready for another massive war and they didn’t want to fight another war, France pretty much from the 30’s to right up to its surrender was in a nearly constant threat of civil war b/t countless groups and tearing itself apart, combined with the Great Depression, and struggling to hold onto their empire, the last thing they wanted was another costly war, Britain was in a similar situation, except for the threat of civil war 2) they did heavily enforce the military restrictions, the problem was that the nazi government Essentially covered up, lied, hid, and mislabeled produced equipment so the allies wouldn’t realize what they were doing, even to the point where had a Agreement with the Soviets that they could test “tractors” (read tank prototypes and ideas) in the Soviet Union away from the prying eyes of the British and French in exchange for oil and rubber, and a major factor was for a good deal of the interwar years the French occupied the Rhine valley, essentially the industrial heartland of Germany, as a way to cripple Germany’s ability to produce anything they’d need for a war 3) when Germany revealed the military they’d built up in secret a few years before the war, it was mostly as a show of force(sidenote the Wehrmacht shouldn’t have done as well as they did, they weren’t prepared for a war against even one of the three biggest economies in the world, they were running out of major resources such as oil, rubber, vehicles and manpower during the invasion of Poland, the literal beginning of the war), plus the allies both absolutely did not want a war, and hoped for peace