I'm going to respond sort of in a reverse order.
2. What did The Dock know, and when did he know it?

?
So, I had no prior knowledge concerning this morning's development. In that, I did not have an inkling that
this was going to happen before the Cardinal announced their planned departure.
The Cardinal schools (BU, Rosecrans, FC, FCA, Miller, Millersport and Grove City Christian) were in talks over the summer to form their own league, and, had the Ohio schools not announced their own defection first, were in the final steps of announcing their departure as soon as next Wednesday. Because this impending departure was going to logically force Harvest Prep into the Ohio Division, there was a pretty solid understanding that logic was going to end up putting Harvest Prep and Wellington back into the Ohio Division with those schools -- which would have caused the Ohio Division schools to leave in response
after the Cardinal. A chain reaction.
Prior to the May meeting this year, there was an understood threat by the Ohio Division schools that they were going to leave because the motion to put Harvest Prep into the Ohio was looming and stood to pass. The key theme and central argument behind the Ohio Division's original plan to leave
then is the same one that stands today: "autonomy; wanting more say over who comes in and who goes out."
Now, what had changed the Ohio Division's decision in May was the combination of two things: 1) Harvest Prep's move into the Ohio got killed because the votes from the Buckeye Division to 'red-rover' HP into the Ohio didn't come to fruition; 2) at the May meeting, there were approved changes to the Mid-State League's constitutional language and bylaws that by default were going to prevent 'red-rovering' (my words, but I'm sure we understand the concept) in the future. As many of you recall, there was a big 'red-rovering' controversy in December where the Wellington School was sent over to the Cardinal Division on a 13-9 "yes" vote where the Cardinal Division as a bloc comprised 8 of the 9 "no" votes. So, for those at home, that situation was about to happen with HP at the May meeting but the Buckeye didn't cast the clinching votes to send HP into the Ohio over like they did Wellington into the Cardinal -- and since-approved changes to the bylaws in May meant that there was never going to be a possibility for that to happen.
As for the "why is the Ohio Division leaving now, despite the May meeting working toward their stated and unstated interests": to reiterate, when the Cardinal Division was crossing the platform to enter the train out of the Mid-State League this month that was virtually going to cause either a big realignment across the board or a simple "sorry Ohio Division schools, but HP (and Wellington) need somewhere in the MSL to play and you're going to be left holding the bag."