When is war popular? So we can only try to stop world wars if they poll well? And the things that he "correctly" did were partly responsible for Pearl Harbor.
Right after Pearl Harbor war was extremely popular. Not only did the Senate/House almost unanimously favor war but donations for the war came piling in.
Japan was attacking the US no matter what. The camps were awful, you'll never get me to defend FDR there, but they attacked because we (correctly) didn't let them control the Pacific for resources. Freezing their accounts didn't help but even if we didn't they still needed to expand and they couldn't do that without going to war with us.