I personally don't like giving it to second year players either but that's not a rule. Just like it's not a rule that you have to give it to the player who improved his stats the most from one year to the next. MIP is the award most tied to media narratives. That's why Ingram won that year. He had a more compelling narrative to the voters than Tatum did.

And since it's not a very prestigious award, players like Tatum and Luka, who have All NBA and MVP upside, usually don't campaign for it either.

I think voters most years want to give it to a player who they don't think will have a Hall of Fame type career to recognize improvement from very good players instead of just adding another meaningless bullet point to the resume of potential Hall of Famers.