A couple of things to note. AWB can be used as a bot but mostly its used in semi manual mode. Although it does help to greatly increase the speed and efficiency of ones edits it also is just one of many tools, like twinkle, Hotcat and a variety of others whose edits are counted. I would also note that I question the data somewhat because Rich Farmbrough did a lot of edits himself prior to being banned from automation so I find it hard to believe that there was only a modest drop. I doubt that the remaining editors did enough edits to offset that loss and certainly counting bot edits we are missing out on a lot. With that said, the corps Wikipedia site seems to be operating progressively slower with each new release so that IMO is at least part of the reason for the decline. Also, the tabs tend to jump around a lot on slow connections so editors not familiar with the site get turned off rather quickly by have to play chase the wild button around. I have had multiple potential editors tell me that they got fed up when trying to make an edit because the buttons kept jumping and instead of hitting the talk or edit button they hit something else. A variety of other factors also impacts things but I'll leave it there for now.