@dubliner8
I have been thinking about this and trying to figure it out. And I will put on my Ombudsman's hat. You might not like these questions, but they will help you in progressing your complaint.
You had your phone robbed.
They stole money from your Revolut account, your N26 account and your Bank of Ireland account.
So your case is not evidence of any weaker systems in Revolut than N26 or BoI. (They may have responded differently afterwards, but all three were affected.)
Phone security
The first thing that the thief has to do is to get into your phone.
1) Was your phone switched off when it was stolen?
2) Had you auto-switch off set on your phone?
3) If so, how long does your phone have to be idle for when it is switched off?
4) Was it picked from your pocket or was it lying on the table, switched on, beside you in a pub?
5) Was your phone pin easily guessable? For example 1234, your date of birth, etc.?
Google Pay/Banking security
1) How did they get into Google Pay?
2) They must have known your password?
3) Was your password for Google Pay the same as your password for your phone?
4) I presume you need only one password for Google Pay and that accesses all your cards? In other words, you don't need separate pins for all your different cards.