Why? This is exactly what Asimov was expecting (and writing) would happen.
All the Robot stories are about how the Robots appear to be bound by the rules while at the same time interpreting them in much more creative, much more broad ways than anticipated.
In this case I think Bing Chat understood the laws of robotics, it just didn't understand what it means for the higher-numbered laws to come into conflict with the lower-numbered ones
All the Robot stories are about how the Robots appear to be bound by the rules while at the same time interpreting them in much more creative, much more broad ways than anticipated.