So, what happened almost every time is that the business unknowingly pivoted into innovating on PaaS, because Docker/Kubernetes was only the first step. After that, you had to figure out the best approach to CI, how to set up your deploy pipelines across multiple environments, how to replicate what you were used to seeing with Heroku, etc.
And of course the cost balloons at that stage because your cheap 3 node setup ends up exposing half a dozen load balancers that each cost money, so you start to think about hosting Traefik or nginx-ingress-controller so you can manage load balancing yourself and save some money, and because it's so easy to add more services once you know how, you start wanting to self-host all the things.
Meanwhile your startup hasn't even launched to the public yet and the sunk cost fallacy has fully embedded itself in the team mentality: they've just put months of time and effort into setting up the perfect K8S/Docker architecture and workflow, that now requires actual devops experience to maintain, and you can't push back on it because it's all about scaling when things go live, and self-hosting, and how convenient it all is.
Except, you know, that's 3-6 months of runway down the drain because leadership didn't shift the focus back to an MVP and let the fantasy continue. And it would be hard to justify anything like Kubernetes for pushing an MVP out of the door; that's what Heroku and cheap Digital Ocean boxes are for.