Justin Welby got called out when Meghan lied on the Oprah interview "revealing" their "secret marriage" days before their wedding. Welby kept quiet for 10-14 days before denying any secret wedding occurred. He got a lot of flack, which he deserved. He's probably playing it smart and staying out of any of the flack. lest he be attacked by his own critics.
I'm sure he's quiet due to allegations of his knowledge of a terrible case of sexual abuse and not acting on it, that could blow in his face also,