My pear tree has these vertical fissures in the bark. I pruned it way back a few years ago, and I can’t tell if the fisures are just the transition from a small diameter branch to a large one or if they are a disease actually tearing the bark.
It might be physical damage to the tree, and it may or may not have gotten infected after that. It looks pretty similar to trees I've seen that were injured when they were young by rabbits, rogue weedwacking, etc.
When you reach your lowest point, you are open to the greatest change.