1. We thought that private clouds were generally valuable. In 2010 it seemed like everyone was going to have a private cloud. It turns out if you are a midsize business, having a rack of "cloud" doesn't really offer you much benefit over having a rack of managed vms. You still need to pay someone to manage that rack. The vast majority of the benefit of cloud comes from having a ton of workloads, which means a public cloud or a huge service-provider sized business.
2. We focused on community building by supporting all use cases. The best way to build an open-source community is to bring everyone in. The community grows fastest that way. Unfortunately, it also means that the product quickly becomes an unfocused frankenstein that is decent at everything and good at nothing. Projects like docker and mesos are suffering from the same problem.
The end result of these mistakes OpenStack is good for certain use-cases. It does really well in large companies that need a public-cloud like environment to manage their infrastructure and can hire a team of people to manage it (e.g. comcast, verizon, e-bay, wal-mart).
I don't know that the exodus is due to endemic problems so much as the market finally waking up and realizing that public cloud is the future.
You folks popularized a misconception and hoped to monetize it in perpetuity and were eventually corrected by reality. So goes all big $$ software.
Get ready for the next big thing and first step that...ad nauseam.