To put it simply motor amps is low end torque and battery amps is top end torque.
At 10% rpm the motors might draw 20 amps at 10% voltage from the ESC and there will be a load of 2 amps on the battery.
This thread is helpful. Another example at 40 motor amps at 50% rpm the battery only has to output 20 amps. On the graph you can see where torque gets cut off in the top end by battery amps.
Controller amps is also important, a bigger motor or battery isn’t exactly more powerful it can just go for longer without sagging or heating up.