I don't think the issue is that people are stupid. Selling single payer effectively requires a great politician and messaging movement to calm understandable fears that people will lose their good private insurance plans, and that the tax increase won't be a net loss of income. I don't think Obama could do that, so why would I trust that Bernie fucking Sandahs could.
And let's not forget single payer failed in Vermont. Sanders can say it was the governor's fault all he wants but his office was involved in trying to make it work; if it had, it would have been a major boon to his future presidential campaign. Instead it failed.
Ultimately a public option is the superior idea, and guess what? Obamacare paves the way for it. The easiest way to do it would be to increase the income threshold limit for Medicaid to around $70,000-80,000 depending on family size and greatly increase government reimbursement rates for services. Then take a page from Stringer Bell and change the name from Medicaid to something else.
Very weird to see Sanders and his supporters outright dismiss Obamacare. But maybe it's not weird and is par the course for his bitter, entitled absolutist mindset. Whether you like the law or not it has significantly cut the un-insured rate, and would cut it even more if not for butthurt republican governors not expanding Medicaid. It's hilarious that these idiot liberals don't realize the law is basically a trjoan horse for the government takeover of healthcare they crave.