My observation on the artstyle "change" claimed: I think this is not a change so much as rushing work and/or taking on too many simultaneous projects. If neither of those, a change to make their own work take less time.
Seen this before with other artists. I think one artist was pochi goya (last i remember, she started vtubing. I recall the art for her manga and related H version taking a dive.)
The other I recall was the one for gal gohan that now has some other story about genderswap. That was a very blatant case of author/artist overworking herself, toward the end of gal gohan it was noticeable. Her new series also is far more minimal in detail compared to her previous work(s).
Don't blame any of them. Unless they are a runaway success and already earned big money, there is a cost of living. Nevermind a desire for fun with earnings. And passion levels dipping over time. Nevermind repetitive stress injuries being possible as constant use + age catch up.