Once the war started, Lindy volunteered to fly against the Japanese, but FDR wouldn’t let him. Despite that, he still flew on fifty bombing missions against the Japs in an unofficial capacity.
Also, his relations with Germany, allowed him to gain valuable intelligence on the state of the German Luftwaffe.
Yes, he was misguided, and even anti-semitic, but back then anti-semitism was much more acceptable in this country, than it is now.
And he was pro-Germany, in much the same way that certain Americans today are pro-Castro or pro-Chavez. He was not alone in this -- the isolationist movement was politically quite influential.
What Lindbergh did, was to give them a famous face to put to their political position.
In many ways, America's isolationists were the other side of a coin bearing Neville Chamberlain's portrait.