Spock spent Discovery season 2 learning to deal with feelings and his humanity. He learned to trust and love Michael again, to reach out to her and depend on her.

And then she is ripped away and he can literally never speak of her outside of his family again.

That kind of trauma might get a person to: Become closed off, not deal with their feelings, re-retreat into their Vulcan side because everything about being human hurts like hell and the one person that loved you and understood is gone forever.