Shot placement is ALWAYS paramount. Until we have handheld phasers, shot placement is all that matters.
There's no way those bullets hit vital areas and failed, shattered or did not penetrate at 30-30 velocities. If you're going to shoot deer with a varmint bullet, 30-30 velocities are what you would want. Fast enough for penetration, slow enough to not blow the bullet apart.
These aren't Water Buffalo. Deer are easy to kill. I know how tempting it is to blame something besides the Nut Behind the Butt.
I don't want it to be my fault when I make a bad shot either. I took a 125 yard shot with a Savage ML10-II, that's known to shoot solid groups at 200 yards. I was seated, elbows on knees, 12x scope. Deer was quartering toward me slightly, head up, calm and stationary.
The only variable is really the shooter. The gun doesn't change. Wind is inconsequential at the speed it was, at that distance and target sizes. The deer was calm.
The screw up was mine, not the gun or bullet.
I'm not trying to be mean. It's just realistic. The OP says "...and there is no doubt about shot placement." Sorry. There is doubt. The deer wasn't recovered. Shot placement is pure speculation and is, truthfully, THE doubt.