Si Ren did not kill Wang Weishan; instead, he destroyed his physical body, extracted his soul, and temporarily imprisoned him in the Flame Prison to be punished.
The reason he chose to spare his soul was mainly to see if the person behind Wang Weishan would risk going to the Flame Prison to rescue him. It could also be considered an alternative way to lure the snake out of its hole.
As for the others, such as Wang Zhe and the direct and collateral branches of the Wang Family, there was no need to keep them alive. They were sent to the Underworld first to stand trial, after which they would face strict and severe punishment.
Chapter 1495