Well regarding the Diana and English remarks - I call baloney that she doesn't speak it, she not only was born in the US, she was training pre-pandemic in Michigan, and I doubt a reporter like Brennan is unaware of that so it comes off like an attempt to deflect answering and Brennan is a reporter so she attempted to push the subject.
It is not hard for me to believe Gleb that Diana is not comfortable being interviewed in English.
For one thing, in response to Brennan, Diana ultimately managed to say in English only, "I'm happy."
Diana did not manage to express a more complete thought along the lines of, "I'm happy with how we skated today," or "I'm happy to be at the Olympics."
(Surely Diana did not mean that she is happy that a cloud is hanging over her mother and Valieva.)
For another thing, in my capacity as a volunteer at JGP Lake Placid, I had a brief interaction myself with Diana and Gleb (nothing like an interview at all).
I asked Diana a friendly question in English (a relatively simple question, IMO), but she did not attempt to respond.
IIRC, I tried asking a second time (again with a smile and a friendly tone), and she still did not respond.
Gleb was nearby, and he calmly/politely stepped in to give me the piece of information that I was requesting.
I got the impression that it is their modus operandi for him to speak in English on behalf of the partnership.