So if it wasn't obvious, pretty big spoilers ahead.
At the end of the book...
Ozymandias teleports a genetically crafted alien creature into cities around the globe, killing millions in an attempt to stop the nuclear holocaust by giving the U.S. and Russia a common enemy in the aliens. He attempts to destroy Jon, but fails. Jon leaves of his own accord in a desire to create life afterwards. Ozymandias questions his own actions momentarily.
At the end of the movie...
Ozymandias does almost the same thing, but instead uses Jon as the common enemy. Jon leaves for the greater good (and to create life). I don't think there is an attempt at destroying Jon. I also don't remember if Ozy felt unsure of his decisions.
Is there an out of universe reason the ending was so different in the movie? Did anyone say why?
This answer explains in logical terms why the movie was different, but I'm looking for quotes from directors, writers, producers, actors, etc etc. The linked question is 4 years old and has no official quote from anyone.