The Battle of Britain would not have been fought at all if they had held the line in France and the Blitz would not have worked very well with even fewer MkIIIs and MkIVs against the commpetitive French tanks.
Chamberlin’s cave-in also was a terrible blow to the German opposition to Hitler. The “success” the Nazis were able to brag about undermined the aristocratic military opposition to Hitler until the tide had turned against the Germans.
If I believed war could have been totally averted by a show of strength in 1938, as some people seem to, I could understand people wanting that. But my belief is that nothing was going to stop Hitler going to war. So it made sense to actually get the preparations to deal with that as close to completed as possible, before going to war, especially as so much improvement was going to occur between September 1938 and early 1940.