This submission is an armbar off of a failed lasso guard sweep - 4. After securing the lasso and sleeve, pulling the opponent’s arm across the body, and attempting the sweep, the opponent may change angles or sink into the mat to avoid being swept. This leaves their arm with the sleeve control open to belly down/rolling armbars.
With the opponent’s arm secured across the aggressor’s body, the aggressor can maintain a pull on the arm, keeping it straight and easier to finish the attack. From here, the aggressor can lengthen their body away from their opponent, making it easy to throw the non-lasso’d leg over their opponent’s arm and roll into the belly down armbar position. From here, the aggressor can finish the armbar, or continue rolling, forcing their opponent to do a forward roll and land in a classic armbar position.