http://ca.news.yahoo.com/s/afp/100111/canada/canada_attacks_justice_trial
They do it because it is what is required of fundamentalist islam
Actually he was planning to sell stocks short just before the blast, figured he would cash in. He said it was to finance jihad in other cities, but my guess is he was going to keep a cut for himself. He expected to cause about 1/2 trillion dollar loss to the economy.