What are the causes of jaw abscess/bone loss and subsequent tooth death, with no trauma, cracking, etc?

Gum disease: Gum disease (clinically called periodontitis) can cause all of those problems. It is an infection of the gums and bone around the teeth, primarily driven by poor oral hygiene but having numerous other contributing factors. It results in jawbone loss, abcesses, and sometimes even tooth death and loss.

Periodontal disease: A slow tooth death usually is a result of periodontal disease. A fast tooth death usually is a result of a carries spreading into the nerve. These are common reason for tooth death, barring any trauma, cracking, etc... See your dentist and have your oral health exam.