Netflix really wants people to sign up for its service, especially as there's a lot of increased competition from competing streaming services. The latest attempt to try and get people to sign up is to make the first episode of The Crown's third season available to watch for free. No subscription required.
Obviously The Crown has been around for a while, but the third season will feature an all-new cast after a bit of a time jump. The characters are older than they were in the first two seasons, but the actors haven't quite caught up, so newbies were brought in.
Obviously the trick here is try and get people invested in the series and make them sign up to Netflix to watch the rest - including the previous two seasons. And considering The Crown mostly appeals to older audiences, it's likely Netflix hopes to rope more of them into the world of streaming. After all younger people are probably subscribed to one or more services already, and would be a bit harder to bring in.