Housing prices are only up 20% now from 2008 because 2008 was the peak of the housing bubble. I can't find charts for commercial lease space, but it was probably similar.
That doesn't answer all the issues you brought up by any means, but do realize further that not only were property prices very high in 2008, they were climbing at a scary rate, so depending on just when in 2008 a deal was done, many would have felt relieved to nail down a longer term deal at the current rate.
Further, just because they found another space that was much cheaper doesn't mean it was a comparable space. From what I see in listings for the wider Bethesda area, there is a very large range in lease rates. Not quite as large as the drop you describe would accomodate, but about a factor of two anyway. Was the cheap new space also smaller?