"... I mean, come Bill D they've had the best part of 5 years to find it."

The real hard evidence necessary to either impeach OR indict & and convict has come to light only slowly....it's not as if they (Bush & Co.) published daily updates on their shenanigans! And, to repeat...it takes VOTES to proceed with an impeachment process, even after the basic facts are known.
Up to the last couple years, it was the usual routine for Bush et al to assert "just bad intelligence" or "unilateral behavior at lower levels" to explain invasions, torture, and other transgressions. Being confident that you KNOW where ultimate responsibility lies is not the same as PROVING it. Our ultimate fallback was the election, and we DID use that. I do, as I said, hope that prosecutions WILL follow next year...but I will not hold my breath.