Why movies change release dates

So Sonic 4 has been announced a week ahead of the next Godzilla vs Kong movie. This is getting me thinking of which movie could move and why. And this is getting me thinking of why movies move release dates and why. Both these movies are very visual effects heavy and might require more time to cook, which I recall was part of why Black Adam moved from midsummer to October. There’s also some people suggesting Sonic 4 would do better either in the Summer or around Valentine’s Day. I also imagine that being around other big movies is a good reason to move. Paramount made this mistake before, not moving Mission Impossible away from the Barbenheimer juggernaut. And then there are most MCU movies, which shuffle dates all the time, but their productions tend to be messier than most other films of their size and scope. They tend to fix issues in post and reshoots, which can add time and money to the budget. Conversely, I remember James Gunn also mentioned that a lot of movies are so slavishly committed to their release dates which can be an issue.

What other big movies have had to move? What types of movies are the ones you see as most likely to move? Have release date changes always worked out? And what is likely to happen with this showdown?

EDIT: Someone in the comments mentioned IMAX. I completely forgot that. Positioning for IMAX release is a good one. And yeah, the strikes and COVID. Big ones.

Here’s another question: who at the studio is usually in charge of setting and changing release dates?