As @Rocko says, he’s reportedly wanted to leave for a while. He changed agents around the time he signed the new deal in summer 2023 but not making the WC squad in winter 2022 apparently stung & he wants to play in a higher profile league after giving Celtic 3.5 seasons.
Separate to that, I always got the impression Rodgers wasn’t fully taken with him despite his qualities & goals for Celtic - see post above. Rodgers seems to prefer a different profile of striker - a more rounded player with strength & other attributes like Moussa Dembélé. Kvistgarten (spelling?) might be more along those lines.