Yes, McConnell was a big factor, but Democrats went along with him, and that was probably NIMBY-related https://www.npr.org/2009/05/20/104334339/democrats-block-funding-to-close-guantanamo

WELNA: Like Majority Leader Reid, Indiana Democrat Evan Bayh is up for reelection next year. He, too, opposes sending Guantanamo detainees to the U.S.

EVAN BAYH: We have a supermax facility in Terre Haute, Indiana. I don’t think the citizens of my state would look too kindly on having those folks housed in our state.