You arse, you do realize that the damned rocket (the thing that actually failed) was NOT - I REPEAT NOT - built by NASA. It was built by Orbital Sciences.

Taurus was probably chosen because it was cheaper than the Delta II (since the satellite didn't need the full capacity of a Delta II), was available, and fit the mission profile. It has had 5 or 6 successful launches, including launches for the Air Force/NRO, so it was a proven vehicle before this. The A-train constellation (which OCO was going to join) is a high inclination orbit (98.2 degrees), so Vandenberg was used for the launch site.