Fans will come back, this is momentary show of disappointment.
Regarding change of captain, I'm hearing Hardik put demand that if they'd make him captain then only he will come back to MI, MI asked Rohit if he'd be willing to play under Hardik, he said yes.
https://crictoday.com/cricket/news/hardik-pandya-agreed-to-return-to-mumbai-indians-after-owners-assured-him-of-change-in-captaincy-report/
Said by 'report' so it may or may not be truth.
This said event happened when India was playing the 50 overs World Cup and Hardik was unfit to play due to his injury. While everyone was praying for him to get well and join the team, he was busy with his agenda. There is nothing to go after the money, fame, and position, what is wrong here is how he did all of it to get what he has achieved. If the MI team agreed to all his demands then they might have asked something from him in exchange.
The bilateral ODI series between India and South Africa will start today under the captaincy of KL Rahul. He has been the captain of the Indian team in the past which did not work out well. If he can win this series then his prospects of becoming the permanent captain for the 50 format will be high.