The ST became the king of MIDI.
The Amiga was the queen of gfx and video.
Machintosh created and ruled the DTP revolution.
Still, they had so much in common. If the three companies had made one OS and all standardized on the Amiga chipset, they could have won over the IBM PC.
Of course, back then, they didn't know how the PC would crush them all, at that time the three thought they were each others biggest competitors.