If you found the ending to season 2 of Bridgerton hard to fathom, with Penelope’s voiceover as Lady Whistledown, you’re probably not alone. The scriptwriters were merely trying to maintain fidelity with the book from which the script was adapted.
Julia Quinn is the author of the book The Viscount Who Loved Me, from which Bridgerton was adapted. She made use of epilogues to detail events that happened but which she failed to chronicle in the book itself.
Most authors do the same. And in the case of a series, it should give clues what might follow or clue the audiences in on what has happened and what they should expect. The ending to Bridgerton season 2 would likely have been different without the epilogue.