They don't need to offer high interest rates; they just need to copy what they are doing in Spain with for example their current account which is free of charges and pays modest interest interest on your day to say current account balance.
With current accounts, savings, credit card, loans and even mortgages they would offer the whole product spectrum, the only difference being they don't have physical branches.
They have some unique features in Spain like a card that can be used as debit and credit depending on what side you use, or as charge card and credit card depending on the side of the card you use.
There offerings are miles ahead of Irish Banks, so if they offer the same as they do in Spain this is going to be a nice addition to the market with more maturity than let's say Revolut UAB.