Normally, in order to solicit a project of any appreciable size, (over 100K) the government is required to produce a detailed SOW (Statement of Work) that defines the scope and goals. As projects get bigger (over 100M) the SOW begins to get more and more generic, but the accompaning Work Breakdown Structure (WBS) gets more detailed, and much much longer (five, six, sometimes as deep as eight or nine sub-sections) Each sub-section may generate dozens of Task Orders (TOs). Task Orders are what get assigned to contractors to work. If the upper document is vauge, or poorly thought out, or poorly defined, then the individual TO may be nonsensical.
Okay... so who is writing this nonsense? Well, the Government can't have the contractors who will be doing the work come up with the work they will do. (That's putting a fox in the henhouse.) So the Government will sometimes turn to a special type of contractor called a SETA (Scientific Engineering Technical Adisor) or FFRDC employee (Federally Funded Resarch Development Center) to develop the approach and SOW, WBS, and sometimes even write the TO. A SETA or FFRDC is specially recognised in that, they (and their respective employer) are expressly forbidden from bidding on or performing work on ANY project for which they have acted as a SETA or FFRDC. It's a classic case of conflict of interest. And, usually these guys are pretty good. There was no SETA or for the Healthcare.gov website. It wasn't considered a "technical" project (like building a moon-lander) so... that was probably the first mistake.
The second mistake is that the people in Government who normally get tasked with writing the RFPs SOWs and evaulating them are usually the same people who aren't um... "smart enough" to figure out how to get out of it. (LIke the jury-duty joke) They's also the same folks who get tasked with evaulating the proposals that come back... again... not the sharpest tools in the shed. So... there's plenty of blame to go round.
The absense of personal accountability in Government encourages irresponsible behavior. But, too much accountability encourages paralysis. (I'm not signing off on that!) So until we figure out how to fix that too... well... this is just going to keep happening.