How on earth were they successful?
Just saying.
Yes they were awful but it's the social history of the time. Remember what Ireland was like in the seventies? The Show Bands, the Country and Western, Big Tom and the Mainliners, Brendan Shine - aaaargh! Ok we had Rory Gallagher who was outstanding but apart from Thin Lizzy we didn't have any bands. Also the Boomtown Rats were not only 'modern' and slightly punky but they were
young so the kids felt this was 'their' band. And Bob had great energy and a kind of charisma. He was incredibly mouthy at a time when young Irish people didn't talk back to Mammy and Daddy. He said all the things they wanted to but didn't dare. You could bring affable, always smiling Phil Lynott of Thin Lizzy) home to meet your Granny but not Angry Bob! The Boomtown Rats were a novelty and they filled a niche.
Then of course the UK picked up on them, I suppose the record companies needed more 'new wave' bands. Loads of dross gets signed up that way. So once the publicity machine is behind you, you're sorted. I remember the first time I saw the Spice Girls........I was speechless. They were a total embarrassment but there you go Roz, that's the world of show business!