https://en.wikipedia.org/wiki/10BASE5 gives a succint but vivid description of the physical layer of the first version of Ethernet and its subsequent replacement:
10BASE5 (also known as thick Ethernet or thicknet) was the first commercially available variant of Ethernet. The technology was standardized in 1982 as IEEE 802.3. 10BASE5 uses a thick and stiff coaxial cable up to 500 meters (1,600 ft) in length. Up to 100 stations can be connected to the cable using vampire taps and share a single collision domain with 10 Mbit/s of bandwidth shared among them. The system is difficult to install and maintain.
10BASE5 was superseded by much cheaper and more convenient alternatives: first by 10BASE2 based on a thinner coaxial cable, and then, once Ethernet over twisted pair was developed, by 10BASE-T and its successors 100BASE-TX and 1000BASE-T. In 2003, the IEEE 802.3 working group deprecated 10BASE5 for new installations.
Usually with information technology, the first version is simple and low-performance, and later versions are more complex, so the above is mildly unusual in that the first version was complex and high-performance.
But it is unequivocal that the coaxial cable of the initial version was superseded by twisted pair. Given that computers had been communicating over twisted pair since the sixties (with e.g. terminals, via RS-232), it seems surprising that there was a digression to coaxial before returning to twisted pair.
I remember in the old days, it seemed like the bus topology was the simplest and most efficient. I was surprised when later, the star topology turned out to be more so.
Did it also seem that way to the engineers who designed Ethernet? Is it a case of 'yes, we had to try it that way to find out it wasn't the best option, but if we were doing it over, we would go with twisted-pair star topology from the start'?
Or is it a matter of bandwidth? The electronics of the time could not deliver ten megabits per second over twisted pair, and a separate coaxial line to every client machine would have been too expensive, leading to the bus topology?
Or is there some other consideration I haven't thought of?