Didn’t Abraham learn the first time? What the heck did he think was going to happen this time? Maybe he just goes around telling everyone that she’s his sister? Maybe he’s just an ass and likes to screw with people, knowing full well that God will plague anyone who takes his wives.
More than likely this story is just a variation of the other one and both got included. In any event, the results are predictable, if slightly different.
This time God speaks to the king and lets him know that he screwed up, threatening him. The king pleads for his nation, despite the fact he was the only sinner. I guess the LORD is like the mafia, killing whole families and such. God then reveal that he knew the whole deal was going on and even kept the king from touching her, keeping him innocent. So why the threat?
Abimelek asked Abraham “WTH?” He wanted to know why Abraham would lie and let his nation be threatened for someone DOING NOTHING WRONG? Abraham thinks everywhere else is so evil that they steal wives, so tells people she’s his sister. Like they don’t steal sisters, right? These nations that don’t fear God (Gen 20:11) will take a wife, but taking a sister (which is perfectly normal and allowed up to now, apparently) is something they won’t do? Nope, not buying!
So, God had afflicted Abimelek’s houswhold with childlessness, so I guess this was something that wasn’t just an overnight affair. After the King paid with silver, Abraham prayed and God fixed it all.
The art of the shakedown, if you ask me!