For some reason companies and individuals believe they can just jump right into ACA and develop a website that can meet all the requirements. That is not the case what so ever. Integrated Eligibility systems have been around for 2 decades, and there are teams that specialize in them. Just because it is a website, doesn't mean it is easy. You have historical legation that you must understand, then you have state specific customization on gray areas of the law.
These systems can range from 500k to 6 million lines of code. For a company to come in and produce the average, 3 million lines of code, within a year, including the entire SDLC process is insane. But that is what ACA was. The federal system had 3 years, but some of the states started late and only had 1 year from start to finish.
Summary: ACA was high risk, if you didn't know what you were doing.