What if Discord was never reformed and is simply biding his time?!!!
(I don't really think this, I just like making up shit.)
Actually, that's a running fan theory with decent credence behind it. Not exactly implausible.
That would make an awesome twist.
He would have the perfect cover as nopony would want to question friendship, plus, one of the popular things fans
bitch criticize about Discord's redemption is how fast he changed from good to evil and how contrived it seemed.
This would explain that.
Hell, it could potentially explain why Discord surrendered to the EOH so easily, he had already had a backup plan!