Why did Meghan Markle and Prince Harry choose to spend their Christmas at home?

Prince Harry and Meghan Markle spent Christmas in California with their children and Meghan's mother despite an invitation to the UK. Meanwhile, the rest of the royal family attended Christmas mass at Sandringham. This year has been challenging for the royals due to health issues faced by King Charles and Kate Middleton.

Why did Meghan Markle and Prince Harry choose to spend their Christmas at home?
Prince Harry and Meghan Markle spent Christmas in California with their children and Meghan's mother despite an invitation to the UK. Meanwhile, the rest of the royal family attended Christmas mass at Sandringham. This year has been challenging for the royals due to health issues faced by King Charles and Kate Middleton.