And Hitler would have backed down.
That's known. However, he did a great job on all manner of people impressing them with his preparations.
And, there are other factors.
As I've mentioned, the Czechs weren't the only matter facing England. They had trade routes and a Commonwealth to protect. They are a democracy, and the people didn't have the political will to enter a foreign war.
Heck, what was the US doing? Much of it was praising Hitler, the majority was isolationist, and the US refused entry to most Jews trying to get away from Hitler.
Different times, those. It may be too easy to judge their current events in hindsight.