The architectural decision to deploy each customer on their own segmented components to make sure that "no one user’s data to mingle with another" seems to me like a solution in search of a problem.

First, the deployment was on AWS (EC2 and RDS among other services) which was probably already co-mingled with other AWS customers.

Second, when you are selling a SAAS offering, the assumption is already there that you'll build security and multi-tenancy into the app and the underlying infrastructure shouldn't matter.

And 100K/month for a MVP SAAS offering. I'm speechless. I just, I can't even understand how this burn rate passed muster with the leadership.

But Kudos to the team for owning up to it and sharing. Lots of lessons learned here.