IIRC, S&W moved into the ammo arena because Super Vel was selling all the light-bullet high-velocity JHPs they could, and there was still demand that Winchester and Remington were trying hard to ignore. Kind of left the door open for S&W to get into the ammo end of the business. Much of S&W ammo's early loads were very Super-Vel-like.

I'm sure the execs were also thinking of vertical integration of their field.