She never sacked her coach. Richardson was a last minute, temporary appointment, he wasn’t her coach at Wimbledon, she basically appointed him when she got a wildcard. He also made it known travelling around the world, away from his family (he coaches his son) wasn’t something he was overly enthusiastic about doing.
They just had different career paths.
I got the impression she sacked him because she wanted a coach who is experienced mentoring a player on tour.
Explaining her decision, Radcanu said: “After Wimbledon, I was ranked around 200 in the world. And, at the time I thought Andrew would be a great coach to try and I went to the States. Never did I even dream of winning the US Open and having the run I did, and now I’m ranked 22 in the world which is pretty crazy to me.
“It’s tough to have that conversation with anyone, but I need someone who’s had that professional tour experience, and has been through it, and seen players in my situation for many years, going through the same because it’s going to take a lot.”