Music evolves. Prior to about 1970, give or take a few years, there were no bands as we think of them today.There were the so-called "ballad groups" such as the Dubliners who had one of 2 members who would play a few tune sets for variety within programs which were mainly composed of songs. The classical musician and composer, Sean O'Riada, formed a group which played traditional instrumental music with a decidedly classical bias. He had a trained tenor, Sean O'Se sing the odd folk song.
What was missing was an integrated group most of the members of which both sang traditional songs in a traditional way and played traditional tunes in a traditional manner... together with a strong ryhthm section.
There were forerunners in The Johnstons and Sweeney's Men but the first group that really put all of it together was Planxty.
When Planxty broke up, Donal Lunny and other musicians founded The Bothy Band.
What was it about them? First of all, there were a lot of them - with 3 lead melody instruments... unheard of in such a group. Second of all, there were all brilliant individually and the whole was greater than the sum of the parts. Third of all, they played very fast with heavy rhythm while still being acoustic. It was revolutionary and many who would only listen to rock music beforehand found this music very exciting and different.
I was in another "neo-traditional" group at the same time. We were on the same program as The Bothy Band at what was our first folk festival. They were on their first USA tour. It was a tough gig.
All the best,
Dan Milner