Re: Sorry for my ignorance but...
Radar systems use plenty of bandwidth. Same for vision processing. In both cases, the bandwidth will be within a module, not running from one end of the car to another. The heavy bandwidth will be between a sensor and the processing hardware. A vision module will typically crunch a bunch of data from its own camera and then tell other modules (over CAN) something like "hey, there's a pedestrian ahead and slightly to the right". The actual processed information is relatively short and low bandwidth (but still time critical).
On a well designed system, another sensor, maybe a radar, maybe LIDAR, also crunches its data. Ideally it says "hey, I see a pedestrian-sized target 8m ahead, moving at 1m/s from right to left".
Meanwhile, a central system hears both data points and warms the driver to be alert to a pedestrian about to cross the road.
Where module to module bandwidth is important, you'll see CAN-FD or automotive Ethernet (I haven't personally seen flexray, that's our there as well, although I think that was most often used in infotainment).