Seemed to be quite a slow rise for him- he only became a regular presenter in 1988, only presenting 2 in 84, 1 in 85, 3 in 86 and not appearing at all in 87.
Well, I did hear that Bruno's Radio 1 career was a bit touch and go in mid-85 - his shows weren't very good and I think there was a genuine thought that they wouldn't renew his contract after the first year. But they tried him out with a new producer who helped put him on the right track and the shows got a million times better. I presume while that was going on they didn't fancy offering him up for the Pops. That said, it always struck me as a bit weird that Bruno's first regular slot was drivetime, a really high profile gig, rather than working his way up through more off-peak slots.
As for his non-appearance in 1987, I assume that might have been because he was doing drivetime so was always on air when they were recording the show. In 1988 that presumably was less of a problem and Radio 1 were happy for him to pre-record some shows, and then from 1989 he moved off that slot.
Maybe it was also the case that Michael Hurll didn't rate him much, certainly when he becomes a more regular presenter in 1988, it was after Hurll had left. It's clear Hurll and Radio 1 had different opinions about who their favourites were - hence in 1982, Mike Read was very much the biggest DJ on Radio 1 with the breakfast show but only presented Pops a handful of times, whereas pretty much the most frequent presenter that year was John Peel. And indeed Mike Read is soon going to disappear on BBC4 for eighteen months, seemingly because Michael Hurll didn't want to use him. Funily enough when he returns he's a very frequent presenter in 1988, probably his most prolific year since the end of the seventies, despite becoming increasingly low profile on Radio 1. Indeed his last show is in February 1989 when he was barely on Radio 1.