I also wonder if perhaps the bots are winning the war against the security team. 2 years ago this month SE banned far more bots but my sense of the bot population now is that it is worse than 2 years ago:

Data:

Time Period: Jun. 8, 2017 to Jun. 14, 2017

・Participation in RMT/illicit activity
　・Accounts receiving permanent ban: 34,460
　・Accounts receiving temporary ban: 8
・RMT Advertising
　・Accounts receiving permanent ban: 120

=====

And this month:

Time Period: Jun. 13, 2019 to Jun. 19, 2019

・Participation in RMT/prohibited activities
　・Accounts terminated: 5,959
　・Accounts temporarily suspended: 12
・Botting activity (Using any number of third party tools that allow for automation)
　・Accounts terminated: 6
　・Accounts temporarily suspended: 15
・RMT advertising
　・Accounts terminated: 2,051

===

8k now versus 34k then?? I think I would sense that much of a decrease in bot activity.