Curbed interviewed an expert:
They’ve been left unchecked for decades and then you’re adding more vehicles, which weigh a lot more than they used to. Additionally, these buildings are under a significant amount of use. They’re largely open to the elements. They’re often damaged.
...
You warn that cars in the U.K. are getting heavier due to the increased weight of EVs. But here in the U.S. we have much heavier SUVs already that are also going electric: In the U.S. over the last 20 years, vehicle weight has increased 22 percent to an average of 4,156 pounds. In this instance, we have a building that went up in 1925, then was converted in 1957 to a parking garage. It was clearly not engineered for today’s cars. What are those heavier vehicles doing to a building over time?
It’s putting an increased amount of vertical load on these buildings, without any doubt. But the other thing to be aware of is the increase in block parking. So the car park will have been laid out for traditional parking: cars being parked in bays with an access aisle. If the cars are block parked, not only is the car on average heavier than the original design load, but there’s more of them in the areas not designed for it.
(Sounds like there were also some possible problems with adequate inspection and follow-up at the particular structure in New York.)