If I understand the situation correctly the MRAP procurement happened mainly because of the insistence of SecDef Gates as an emergency measure to help to prevent the casualties being caused by IEDs. The standard DoD R&D life cycle model was short-circuited at the highest level because of the perceived urgency of the need.

During peacetime one of the U.S. Army Training and Doctrine Command schools, probably Infantry or Armor, would have served as the "combat developer," performing studies and analyses to define system "requirements." Once those desired characteristics had been defined in a "requirements document" approved by the proper level within DoD or the service, the program would have been turned over to a "materiel developer" (such as whatever the U.S. Army Tank-Automotive Command is called these days). They in turn would release an RFP, conduct source selection, and then develop a prototype. Then testing of the product takes place. The problem with this system is it usually takes 12 to 20 years to put a new item of equipment in the hands of troops.

How Army Ordnance ever developed the M1 Carbine so quickly in 1940-42 doesn't happen very often these days, mainly because our own DoD and service regulations for the development of new systems don't allow us to go from Point A to Point B without performing 35 steps in between. Often many of the documents produced during a developmet program have to be distributed to numerous DoD or service offices, any of which can non-concur and prevent forward movement in the program.