Plotwise...
...this is "King Kong in Rome."
shareIsn't. King Kong was big from the start, Ymir grew and grew. And Ymir didn't hang out with the same blonde chick all the time.
shareWhy the hell would anyone try and study a monster that grows and bullets have litle effect on it???
shareThey explain that - it's so they can study it so they can go back to Venus to harvest precious minerals not found on earth.
What isn't explained is why they keep on shooting it like dopes when bullets have no effect, or even why they don't try and incapacitate it like the first time rather than destroy the precious source of that research.
The answer: idiotic screenwriters.