Too Short -- I Ran From Cops ... TO ESCAPE

Ever since TMZ posted a crazy video of Too Short running from cops during a DUI bust ... everyone has wondered, WHAT THE HELL WAS HE THINKING???? Well now we finally know.

Short was out in L.A. Friday night at KDay's Krush Groove Concert ... when our photog broached the subject, and the rapper fully admitted he ran away from the police because he really thought he had a chance to escape.

But we all know how it turned out out -- Short was arrested and charged with Ecstasy possession after cops say they found drugs in the back of the cruiser.