You're assuming that by freeing those 7--assuming they weren't badly injured during the collision--everyone else on the ship would've been rescued if the ship sank. We'll never know of course, but it's possible that the loss of those 7 may have saved the remainder of the crew onboard.
Capsize is more likely than outright sinking, given flooding on the one side; and, free movement of water in large spaces without baffles to prevent sloshing.
The water temperature was above 70 degrees. A Navy ship has a ton of life rafts that automatically deploy. Abandoning ship is not a problem nor dangerous for a Naval vessel.