It's funny we are all actually saying the same thing, albeit from completely different perspectives! The pro-Adi faction is blaming the writers for butchering his character while the anti-adi faction is personally blaming Adi, which is technically blaming the writers since Adi is not a real person, and is a figment of the writers' imagination! :-)
In a bid to keep the drama going and keep all the characters of the triangle employed and relevant, I think the makers had to bring in the pregnancy angle and tap into the sentiments of maa ko kaise jail bheje nonsense, and hence the very flimsy reasoning that Anu is the one who drugged everyone and Malini is also a victim of her mother's evil scheming. It is still not clear if Adi, after watching the video actually believed Malini did rape him or not.(this is not my defense of Adi or anything, but just pointing out what I think happened in the show!). That is probably the makers' way of justifying Adi's stance about not wanting to send Malini to prison.
At this point, it does seem like either the makers want to or Gash himself wants to reduce his screen space, and in a bid not to lose audience (many of whom are in it for Adilie, let's face it!!), they are trying to butcher his character as much as possible, so people will just give up on him (and possibly Malini) and smoothly transition to Aryan and Imlie while not losing audience.
I don't know if a new set of writers took over after 300 episodes, but they really poorly handled the character arcs of whomever they wanted to butcher by just completely throwing them under the bus - be it Malini or Adi.