Businesses pulling out of the UK based on the Brexit process is bad for the UK, and I'm sure this was indeed mainly motivated by N26's need for a UK banking licence, which is a costly and difficult process to go through. However, it's worth noting that they are pretty small in the UK (~200k users). They're very successful in Germany where banking is a very slow, difficult, manually run industry (from what I've heard)…
>N26 on the other hand just didn't have a compelling offering. They charged for most/all of their accounts (explicit charges for accounts in the UK are uncommon), they lacked features, and their marketing was unremarkable compared to the competition. I'm not buying any of this. I'd speculate that N26 was denied a banking licence in order to look after the "British challenger" banks who already operated in the EU with…
I don't think that's really addressing the point though: Monzo/Starling/et al. are also all free, have a great app and savings up to £85,000 (€100,000) are guaranteed by the UK government.
The fact that they have an order of magnitude fewer customers in the UK than Monzo, for example, seems like strong evidence of their failure to compete; it seems hard to find a compelling reason to use them, especially when they were so late to the market.