Ishihara is the mastermind behind the downfall of the franchise over the last couple years. All grievances related to mobage, killing of the spinoffs, annual game releases etc. are the result of his decisions.

Masuda hates the current state of the franchise. He is overworked and despises the annual release. He hates when shills blindly defend the series because it means the situation at Game Freak will never improve under TPC's tyranny.
Masuda, being the spokesman of Game Freak is a scapegoat. He wants change but cannot do it by himself.
Dexit was never meant to be revealed beforehand. Japan has still not had an official announcement, so then why does the west have one? The reason is that Masuda's Treehouse announcement was non-scripted. It was a means for fans to rally together and express outrage towards the franchise.