It was a lot less ugly than whatever else passed for networking standards at the physical level in those days.

Arcnet, Twinax, Token Ring and so on, I've probably used them all, and at scale. Compared to Ethernet they all sucked, besides being proprietary they were slow, prone to breaking in very complex to troubleshoot ways (though ethernet had its own interesting failure modes in practice it was far more reliable), and some used tons of power which made them unusable for quite a few applications. On top of that it was way cheaper and carried broad support from different vendors, which enabled competition and helped to improve it and keep prices low.