We did the same to the Germans on D-Day. But to say FDR knew that PH was the target is to fall into that conspiracy black hole where FDR needed the US to be attacked to get out of the Depression. This “story” has been going around for years.
He didn't expect PH to be struck, and spent the rest of the war doing political damage control by blaming the area commanders instead of accepting the lion's share of the blame, which he deserved.