I once helped fix up a manufacturing co that materially overstated net income by >10% for a decade. And it was just a mix of honest mistakes, miscommunications, some incompetence, and a shockingly small amount of fraud (though not 0).
I learned it's really easy for sr execs to run the company badly, one or two junior execs to push the limits, and a everyone else to just be a biiiit lazy - and bam, there's a big fraud.
That said 0 stock is up 5% w/w, so this can't be THAT big