The object flies in a straight line up to 90 feet in a direction you choose before falling to the ground, stopping early if it impacts against a solid surface. If the object would strike a creature, that creature must make a Dexterity saving throw. On a failed save, the object strikes the target and stops moving. In either case, both the object and the creature or solid surface take 3d8 bludgeoning damage.
From what is written above, it seems to imply that succeeding the saving throw means the object still deals it's 3d8 damage, but can continue to fly forward, potentially damaging additional targets. It actually seems ideal from the caster's perspective for the enemies to succeed their saving throws if they are in a line.
Is that really what happens? RAI it seems obvious that the spell should not damage targets that succeed the saving throw, but our group is trying to go with as much RAW as possible. You could even mitigate the damage dealt to the projectile by using something especially sturdy, like adamantine.