With the government shutdown, “maybe” LaGuardia was short-handed with traffic controllers. These would have been ground controllers.
Reading the article, it appears one plane had just landed and the other plane was positioning for takeoff. Of course, the NTSB will investigate and the FAA will review their findings and make any necessary changes if needed.
I can’t even imagine how this happened, other than lack of experience or inattentive behavior. It’s just like driving your car out on the highway. We have to keep looking around us and be aware of any possible intrusions. It’s not rocket science, however, traffic or ground controllers have huge monitors in front of them to watch the planes in the air or moving about on the ground.
Just a quick guess is that maybe the landing aircraft failed to turn onto the correct taxiway, or one of the two planes failed to heed the instructions to hold short on a taxiway until the other Delta plane had passed by. Also, the taxiways have detection devices to keep track of traffic. That possibly should have clued someone that two planes on a path of an incursion. It sure sounds like lack of attention, but one never knows. Freakish things happen sometimes.