And it was obvious enough for an undergrad to discover. Even though it passed the (at the time) tried and true methods that proved the fitness of many designs. It even became a cautionary tale that improved our procedures without the building falling down and killing people (which I find to be the truly amazing part of this story).
However, your lego example could point out why wind wasn't tested at the corners. In pushing over legos you assume a constant force from any direction (since you're pushing with your hand/foot/whatever). But wind produces considerably less force at angles. How would you blow over a lego tower? Your first obvious choice might be to try directly at the sides.