Ryanair have crew and aircraft on tap unlike other airlines. When EI divert usually crew are out of hours and they overnight passengers in hotels, Ryanair don't, Ryanair did cancel some flights. Many regional flights were affected which explains a lot while mainline flights were combined as much as possible. From what I saw they were trying to get all T/A passengers out of DUB on 27 Dec and when you lose the first 90 minutes of schedules getting replacement slots at main airports isn't not easy while in F24 one flight to PRG taxed and then found out there route plan had being cancelled and had to do a trip around DUB before they got another. Also what would of being the setup at DUB on the 27 as when flights resumed Ryanair had most of the departure slots first so I expect those were kept before EI were given some. It was close to 9 before many EI flights got out.
However I did see some pics on FB and more staff ahold of being drafted in to deal with backlog