Well they wrote themselves ito a corner. Its the only way you can justify someone walking around after getting exploded.
Though it might not have been an asspull. Remember when Vader betrays him and throws him out into space, and then he wakes up just fine afterwards? My reaction was WTFNO! You can't survive that. But what if he didn't? Get my drift? 😉 I also recall that after he wakes up in the novel he wonders why he no longer has any scars. So this all might have been some brilliant scheme they had right from the beginning. Or just dumb luck.