The individual mandate merely guaranteed a captive audience for health insurance companies. That doesn't do anything for cost. What drives cost is the ACA limiting profits based on the cost of care, thus more expensive care equals more profits. Can you see where this is going?

Five states plus DC still have an individual mandate (ugh), and yes health insurance premiums are spiking there too. A large part of that is due to the tax credits (generously labeled subsidies) expiring – even with an individual mandate health insurance is prohibitively expensive.