I'm assuming you're talking about the Munich pact? Yeah it might've been a mistake but the allies needed time to build up.

In order to attack Germany, right?

I suspect that the soviets would've invaded Germany if they hadn't been attacked first.

This is good.

It seems like all the major allied powers wanted to build up to attack Germany. The only difference was the Soviets saw fascism as an existential threat and the other major allied powers saw them as potential competition.