Why? Most likely money laundering through the campaign. Even he knows he's polling between syphilis and Ebola.
All true but don't forget about Honduras.
I've never been to El Salvador, so I can't speak with direct knowledge, just what I've heard. I know what the program was in the 80's though. Drugs and kids went north, guns and money went south. C-130's, sheep dipped "advisors"…Mena wasn't the only airfield. Interdasting things were unloaded in the middle of the night at a certain SoCal airfield now closed due to ground water contamination. The kind of things that can get you suicided.