Earlier quoted context omitted.
MASH maybe. Burn After Reading and Fargo, not so much. Not that they weren't dark -- just that they weren't a success in any mainstream way, especially the first.
Fargo made over 8x it's budget in income on the original theatrical run. That's major success. For comparison, a traditional american "happy comedy", Happy Gilmore released the same year, made a third less despite costing almost twice as much.
Well, it's budget was a tiny (by Hollywood) $7 million, so that's not saying much.