I think what's common between the three is that, these are the turning points where human minds brought about change out of necessity. The ages before those mentioned are periods of great depressions and unfortunate event. So, these fueled the people to change for the better and appreciate science and art more.
The main reason for the fall of the Mali empire was there system for succession . Since there seems to have been no strict tradition, there were many fights over succession. This led to civil wars and was a big part of th reason why the Mali empire declined.
This is the answer I found it online for you if you need anything answer I would just look it up it really does help :)
