I really think Simba was... being...different in TLK 2. Like a different lion. Way too overprotective... but maybe it wasn't his fault, maybe he was just TOO scared to let anything happen to Kiara
Out of all of the characters from the TLK trilogy, Simba is my overall favourite. I have no clue why, but I think it's his personality or something like that.
He was pretty overprotective in SP, but like everyone else has said, he lost his son. If I had lost my first child, I would be pretty protective of the next one as well!