It was first rumoured earlier this month that Bravo executives had decided to fire Jill Zarin, Kelly Bensimon, Alex McCord and Cindy Barshop from the programme, reports which the network later confirmed.
Frankel, who left the series in 2010, said that she expected a shake-up in the Real Housewives cast as audiences want to see something new.
"I'm not surprised only because it's been the same cast for so many years and Bravo... likes to make changes," Frankel explained to E Online.
"They probably just felt like it was time for a change. People do that in relationships, they do that in work strategy. I don't think it's personal. I think it's really just business."
Frankel was recently lost at sea for close to 20 hours with husband Jason Hoppy off the coast of Massachusetts.