It’s an indicator that this is not a spur of the moment action. They have put some thought into this.
Mrs. Mugabe is not a universally beloved figure. I suspect that they waited for her to make her move, and now can argue that they are reacting to her actions. I think that they planned this out, and merely waited for Mrs. Mugabe to move first, which provided them the justification for acting.
As long as the country does not slide into civil war, the Zimbabwe may be better off.
That's putting it mildly. My understanding is that she is hated by a large chunk of the country. Hence my comment on anther thread that they would shoot Mugabe, blame Grace, and then shoot her...