If you look at their staff growth, it's been very slow and very steady. At the time of acquisition they were sitting in the 100-150 headcount range, which is modest for a company that's almost 15 years old. Given their claim of 207M to artists last year and their touted 18% average rev share, we can guess they were generating around 50M per year gross, which is a very healthy cashflow for a company that size.
Their strategy was clearly not to take over the world, but to carve out a niche and not bother to directly compete with the streaming platforms (which helps to explain, for instance, the incredibly rudimentary mobile player app).
As for the senior management, Diamond had already previously started and sold a company. I'm sure he was doing fine. The same is true of Mark Hall, their VP of Product (who started 5-ish years ago, if I recall). The technical founders I'm less sure about, though apparently at least one of them had already moved on.
I'd absolutely describe it as a sustainable lifestyle business that had a good long-term trajectory. It was never going to be a unicorn, but who cares?
