Digital identities (eID) are one of the crucial building blocks of a digital infrastructure. There are major differences between countries of the European Union when it comes to the success of digital identity infrastructure, yet, we lack insights into the conditions for successful digital identity infrastructure evolution (eID evolution success). Taking the outset in a digital infrastructure perspective, we conducted 18 expert interviews in the context of the European Union with the focal case of the eID infrastructure in Germany. We used the grounded theory method to develop a model of eID evolution success. We discuss how the model can be useful to governments, practitioners and researchers alike.