With a brushed motor set up with a PWM ESC, starting is relatively gentle, the stream of pulses allows the inductive components (ie the motor windings) to produce current limiting back emfs until the pulses get wide enough to move the motor, when it starts to get sensible.
I suspect that the opposite applies with brushless motors. At low speed, a very wide (switched on for a long time electronically speaking) pulse must be applied to get it moving. This leaves the motor coil acting as a pure DC resistor, and a high power motor has a DC resistance of sweet very little. If there isn't quite enough voltage to provide the power to move the motor, it will act as a dead short.
This will result in high start-up currents. If they are over in a short time, the fuse doesn't have time to overheat. Fuses have ratings, normal, slow and quick blow. These give a general idea of how quickly a fuse will react to a current slightly above its current rating. Give a "normal" fuse a few percent more current than its rating, it will take a long time before it blows. Give it twice that, and it blows almost instantly. Put such a fuse through a lot of abuse cycles of heating and cooling, expansion and contraction, and it will weaken, either reducing its current carrying ability, or slowly converting itself into a quick blow, or both.
Just a thought about two in parallel - it is the way of the world that they will not be identical, so one will die off first, probably quietly and gently, leaving the survivor doing the work. You might not notice the first one going, but you will notice the second, because that's when everything stops.