Regarding the idea that SC set up or wished to set up a fake carjacking and real beating, it is possible, but these are my sticking points. If he was planning to set this up, then there's still no viable explanation of why he didn't also set up his broken down vehicle story. Without his story of why Charli was out Hana Highway (to be in position for this supposed carjacking), then no one would believe she just went out there alone after the birthday party in Haiku, after a long day of work and working early the next morning, and very pregnant.
Another point is that carjacking isn't a thing on the island like it is on the mainland, so it wouldn't be readily accepted. I can't remember every hearing a story about an incident like that. What people will go for is when they see a pattern. In this part of Maui, the disappearances of Laura Vogel and Mo Monsalves had set up a local predisposition to entertain the idea that someone may be making women disappear never to be seen again. I do think Steven was pointing towards that, and in the alternative, he suggested that Charli may have angered a person or persons who might retaliate. The latter one might have led to a beat down, it is true. But a beat down on a pregnant woman is not very believable here by the public, IMHO. I just can't recall it happening. Domestic abuse of family members is extremely common though.