When presenting a historical drama that's palatable to viewers and to make the story more interesting, poetic or dramatic license is applied. To present an event in the Crown such as Margaret's romance with Peter Townsend, to have interactions between the cast of characters that were involved (fictional dialogue) can present not only how it may have been but highlight the reasons why Margaret and Peter were deemed unsuited. Same thing with the scene of Elizabeth and Philip's fight early on in their marriage in Australia. The actual film capture was destroyed but it was played out fictionally to provide the information that the the couple didn't always see eye to eye but yet had those filming the event had respect enough to destroy the film.
Otherwise we'd be back in history class where events are droll and repetitive of dates, locations and battles we needed to learn by rote. Historic advisors are the ones for the Crown that assure the factual history is on par with the show. Otherwise it may have ended up that the show had Anthony Armstrong-Jones as the divorced lover Margaret gave up and later married Peter Townsend.
