The Emperor of Germany had a tradition of going out on his balcony and basically raving about whatever was on his mind for anyone listening. Some of those talks were a little crazy-town. Wilhelm wasn't always one to choose his words carefully; he just spoke his mind. Or apparently yelled it at the crowds below or sometimes at the assembled German armed forces.

If you think that announcing unrestricted submarine warfare in the Zimmermann Telegram was a blunt and ill-reasoned military strategy, just wait until you've heard some of what the Kaiser had to say. He was like an overexcited child with an actual military instead of toy soldiers. He recklessly picked a fight with most of Europe that resulted in a humiliating defeat for Germany and led to another disastrous global conflict twenty years later. The German naval brass convinced the Kaiser that unrestricted submarine warfare was a great idea that would have Britain begging for mercy in a matter of months.

You can see why he would have approved of the meddling scheme proposed in the telegram.