Possibly the change could have coincided with humans learning to use weapons regularly during combat. This would have made violence much more deadly and potentially resulted in more violent individuals dying off early.
I think the main reason we haven't seen many life forms evolving long life spans is that the biological cause of aging may be closely tied to other important things. So it may be difficult to evolve long life without some other disadvantage like slower growth.
Another possibility is that aging is actually a side effect of some other important process. This would make it difficult to evolve ways to slow down aging without affecting the original process. My guess is that aging is somehow related to growth rates since organisms with longer life spans like humans or turtles often take a long time to reach maturity. Most forms of life need to reach full size as quickly as possible followed by a rapid stop in growth once full size is reached. Perhaps the rapid stop in growth causes problems with the body's repair mechanisms which ultimately lead to aging. This would be kind of like a business or city which experiences a sudden stop in growth that eventually leads to breakdowns as there is no longer enough money to maintain the infrastructure built up during the growth phase. The physics based theory in the article can't explain why similar forms of life age at very different rates (i.e. dogs aging 7x faster than humans) so something else must be going on.