Everything below are just speculation and guesses.
With the recent changes to ProTour payout on appearance - link here
I would have to speculate for the reason behind this sudden move.
Now connecting the dots i have found the following below:
I believe this all started with the "leak" on a cards spoiler then banning of a handful of judges -
Now this is a red flag for judges (as they are volunteers that can be dispensed by WOTC anytime they seem fit),
opted them to make counter measure regarding matter moving forward,
hence they filled a lawsuit against WOTC. link here.
Now Wizards check everything,
and later found out that Pro Players can also be qualified as an WOTC employee
once Judges win the lawsuit case.
Now to proactively counteract things,
they reduce the payout on Pro Players (supposedly making them look like players rather than Employees.
- if you would look closely on the lawsuit, it would seem that Pro Players are likewise Employees of Wizards
While all of this are all my speculation, and just wild guess.
But who knows, it might be true ^_^