I expect the pressure came from the IRFU.
I don't believe that Irish rugby could risk being seen to condone the attitudes these guys have shown in their messages. Ulster, as a club, might have been able to ignore it all (and the support for them in Ulster is much greater than down here) but once the sponsors had a look they were in real trouble.
I hope this leads to more "outing" of private messages, private chat groups etc etc. I have no issue with kids in particular, but also with adults, having spaces where they can chat privately. But I don't believe anyone would happily chat with their friends and use racist terms in the way these guys showed their misogynistic attitudes.
It's wrong, what they were saying to each other. Like Trump and his locker room humour, it's just plain wrong.