Suppose I should research it and find out. Perhaps the flimsy side of the trailer didn't weigh a lot.
[EDIT: "According to WHP, the troopers had stopped to assist at the scene of a previous crash. As they were stopped with their lights activated, an approaching semi-truck was hit by a large gust of wind which sent the trailer toppling over onto the trooper’s vehicle.
WHP released video of the incident on their Facebook page Friday with a warning asking semi-truck driver’s to follow high-wind advisories and closures. The WHP said even at slow speeds, the gusty wind can blow over a semi-truck. Troopers did not say is the driver of the truck was travelling in a wind-warning restricted area, or if the driver will face any citations or charges." No mention of injuries.]