This was the case with me also, until recently. I must admit that I was subconsciously dismissive, assuming that he was canonized merely for being killed by the Nazis. But when I read about his early life and work, and his devotion to the Blessed Virgin, then I realized what a great saint he really was. Oddly enough, not only was he involved in the European theater of the war, but he also established a monastery in Japan near the site of the atomic bombing of Nagasaki.