Background: There is substantial interest among scholars in digital platforms and the ecosystems around them. Digital platforms are open, continuously evolving, sociotechnical structures that can be sensitive to various changes. Aim: We take one-step further and investigate the post-dominance phase of platforms. The electronic identification (eID) ecosystem in Finland provides a good example of ecosystem transformation due to external changes from EU and national regulation. Method: We engage in an extensive case study of a nation-wide monopolistic eID platform. We first take a retrospective view to understand the historical context and then examine in detail how an external driver leads to changes in the ecosystem. Results: We explicate the platform evolution process, from a phase of dominance with centralized control structures to a more federated governance approach. We find that the introduction of intermediaries between the platform and its users contributes to a weakening of the dominant platform owners. Conclusion: This finding that platforms can transform into industry infrastructures has an important implication for our understanding of the dynamics underlying digital platforms.