I would reframe this as the cause being lack of health insurance and an emergency fund capable of paying the deductible on said insurance plus 6 months of expenses in the event you're not able to work. Those two things don't guarantee not going bankrupt, but I would imagine it would be a lot harder.

Another way to frame it is how well people can bounce back from a medical emergency. The poorer you are, the harder it is to come back to even where you were before the incident.

Medical bills get out of hand but blue collar workers often find themselves out of work, fired because they couldn't make it to work through no fault of their own.

Our society punishes people for being poor and it's disgusting that it's so hard to even get people to acknowledge this, much less try to fix it.

Yea, that's what the E-fund is for. What percentage of the people declaring medical bankruptcy had health insurance and an E-fund to cover the deductible plus 6 month's expenses?

Sometimes this is true. But there are large external factors that determine this other than how hard a person works. The dot-com crash and the recent financial crisis for example.