It's not an easy market to jump into; you spend a huge amount upfront on site construction (particularly if you're building standalone clinics outside of existing medical buildings, which is not unusual for urgent care), labor cost and complexity is high, and reimbursement cycles are long and painful. Healthcare chains scale like retail, not like software, with all the attendant cash management problems.
It feels like they did offer a superior service with lots of effort put into getting into the community, but I question both their decision to try and build a custom EHR -- yes, EHRs suck, but once you start building your own, you're no longer a medical services company, you're now an EHR company -- and not to pursue a regional-centric expansion strategy aligned with local health systems via contract or JV, instead choosing to build a small number of clinics across the country, which goes against proven successful buildout strategies in healthcare.
It's a shame they've gone under -- again, superior service, obviously a lot of care for their patients -- but "we went under because of cash management problems and inappropriate growth strategy" is a pretty standard story in the healthcare world.