Deer moved, or something near/at contact changed path of penetration (or combination of these).
Seen bullets change penetration direction substantially by clipping bone.
Had a doe take a .44 mag 255 cast, broadside to tree, straight down shot. Bullet hit upper rib near spine and exited not at bottom of chest but by her udder.
Had a 9 pt take a shotgun foster slug, again from treestand, angling away, hit near last rib. Didn't go into chest cavity and exit at lower front, it slid to the back of his head, wiping out loins all the way there.