Driving too fast and too much data to process.
Option 1: You're programming a device to scan pictures coming in on a video feed. The FPS is either 60, or even 1. You scan the picture from the top left, down, and move over one column. In an Excel spreadsheet that's A1..A255, B1..B255, C1..C255. Once you get to Z255, you load the next picture.
But depending on how much things change from A1 to Z255, you may need more time. We're looking at things like color / contrast, common shapes and potentially grouping.
The faster you drive, the more likely the system is to disregard frames 3, 9, 11, 12, 13, 14, etc.
One frame at a time, one column at a time.
Option 2: You're programming a device to take pictures coming in on a video feed. You compare the frames between 1..2, 2..3, 3..4, etc. Like a badly compressed JPEG video, you only try to figure out what has changed, and evaluate those changes into objects (e.g. lines, cars, etc.).
But if you're driving too fast, each frame is too different from the prior. The system can't process the differences fast enough in order to ascertain what is a lane marker, a vehicle or a gore point.
This is why a faster processor is necessary, and the more video inputs that are present, the more complex of a picture that can be rendered - and the faster you can overwhelm the system.
Mobile Eye used one camera and a few ultrasonic sensors (plus the radar sensor). The newer versions us more cameras, and ultrasonic sensors that reach out further. But it's still limited by the processing speed of whatever CPU / GPU is out there, and the methodology used in programming.
The moral of the story is to slow down and pay attention. Think like a computer programmer would, think like how the car would process data, and you'll be safer.
Edit: I live off a road with 120-180 degree turns, and the autopilot can handle the entire thing at 25MPH. Speed up to the speed limit of 35 and it'll disengage about one-half through. Speed up to 45MPH that I can handle, and it'll disengage about 10-20% up the hill (or cross over the double yellow and I'll step in).