Over the decades I've rooted out and studied works focused on the fall of civilizations. What - if any - common threads exist at the start - thus end - of a once dominant rule.
You do your own research - by all means. Let's see if you arrive at a similar set of threads.
Me? One consistent thread surpasses pitch-forks. Pitch fork people still have a sense of hope such that they believe their riot will produce results.
When 99.95% of those who were once productive members of society simply give up on life. Who embrace anarchy (as a vaccine for apathy). Who just don't give a F**K any more - well past burying any sense of hope . . . . similar to old-age cascade of organ failures - the body dies.
A 90% flat tax on wealth above one billion solves things over night. No tax havens. No generational tax hand-me-downs. Got more than one billion to include all assets? Pony up.