"Accident rates have plummeted since the computers took over."
Exactly this. Since the 1970s there have been exceedingly few crashes which weren't caused by human factors(HF) - and that's why the study of them has become obsessional in aviation.
HF led to the realisation that hiring ex military fliers for civil transport jobs was a bad idea, because military fliers are trained to press on regardless when they should have diverted or gone around - that in turn led to the establishment of all those airline-funded flying schools and aviation degree colleges, etc
When HF started to be applied on the ground it was realised that bad road _design_ was a major factor in traffic crashes and that drivers pay little attention to posted speed limits - they take their cues from the road design and furniture - and perversely the more "protective" furniture there is (signs, fences, parking restrictions, light controlled crossings), the safer the drivers feel, the faster they drive and the LESS attention they pay to their surroundings - leading to a problem that adding crossings or lights to protect pedestrians frequently results in them being less safe.
Lion Air seems to have thrown HF out the window with the reported requirements of pilot conversion and training (a few hours of PC simulation, vs other airlines requiring actual time in a flight simulatior) and the reported safety culture there is an order of magnitude worse than reports that came out of MAS (shifting faulty kit from aircraft to aircraft instead if actually fixing it, or overriding a safety inspector's grounding order by pulling political strings to get his boss to issue a countermand are actively undermining safety, vs simple sloppiness).
HF is most successfully applied across an entire organisation to find out why safety culture is failing, but in this case I'm willing to bet that it's coming from criminal levels of mismanagement in pursuit of profit above all else.