The Mikage one is really good, i saw part 2 a few days ago... It's probably selling way better than his NTR work, since it will obviously continue, judging by the ending.
I think i also saw like 2-3 more NTR artists going vanilla recently. My only real guess is people got sick of the stale over used plot all of them constantly use, so the sales are not on the level the artists want. It's hard to be unique in that genre to satisfy their fans, while in vanilla it's really easy. Slap a cute or cool sexy girl, do a wholesome setup, profit. Then add another girl for a threesome in the next few parts and profit even more lol
But one thing is funny, all of them reassure the fans on the last page/twitter that these works will stay NTR free... Maybe this is the real "Grapara effect"