I'm sure there were other computer bridge options then, but bridge people are different in the UK. These days it's a fun social game, but at times bridge clubs have been equivalent to masonic temples. It's a strange, complex parallel culture, it's an odd kind of high status (a sort of posh and not posh thing — educated but meritocratic), they would have tended to be older and to have a bit of money. (A town in my area has a very posh Georgian bridge club building and hundreds of members even now)

I suspect there would have been a glossy advertising campaign in the middle pages of the Radio Times that everyone saw, that bridge players would (at least then) have been very considerably approving of the BBC, and that word of mouth and "keeping up with the Joneses", along with bridge partner influence, did the rest.

I would bet that it sold OK and that for a few older Brits at the time, this or the chess companion (which I remember more clearly) would have been their first experience of a computer (aside from Teletext).

It's quite Reithian in that sense.