Porkins met his death due to the fact that he was flying lower then he thought he was. He routinely kept his gravity compensation up a little higher then most pilots regularly did (perhaps as a side effect of being a fatass). As a result, he was unaware of the Necessity to pull up, since he could not feel his X-wing drifting downward, thus flying through the debris of the exploding turbolaser tower. This is according to Wedge Antilis's analysis long after the battle of Yavin in "X-Wing Rouge Squadron".
How can you feel a spacecraft drifting downwards in a vacuum? Did the Deathstar have an atmosphere? A better analysis would have to be: The generous folds of his cheery cheeks obscured the giant metal ball approaching rapidly from beneath.
Lucas just didn't have the CGI technology at the time to pull it off. Look for it in the upcoming 35th Anniversary Special Edition! Porkins even has a musical number after his death.