I can see the logic behind it though.
How did Sterling stop the press campaign against him? He didn't hide away and hope it disappeared on his own, he went on the counterattack, called out the racist undertone to the coverage of him, took on the tabloids and created a national conversation about the treatment of black footballers in this country by comparing the treatment of Tosin and Foden amongst other things.
Since then, he has been left alone, he's been able to have some level of privacy, because it became impossible to justify these articles dissecting every trip he made to poundland or gregg's.
Harry and Megan have waited for the right moment, they've made sure the interview is watched by everyone and headline news around the world, and they've created what will be a national discourse about racism and mental health and tabloid culture.
If the interview works, the conversation/argument will eclipse the pair of them, they will stand to the side and when everything's done, the tabloids will be weary of running negative stories about them because they won't be popular.