The issue of 'how' never worried me: when you believe in a God that can do literally anything, a mass update of the DNA of every carnivore on the planet is just another "blink and it's done" moment.
The issue of 'why' is the one I did not consider until years after I had faded. Occasionally, YouTube would point me to 'nature' videos of the violent behavior of some animal species. They are quite disturbing. Apparently, there are species of pack animals that will wait for a pregnant female (say, a deer) to be in labor pains, and then they attack, literally ripping the offspring from her body and dragging it away to eat, leaving the mother badly injured and in shock.
And those aren't the most disturbing videos you can find. I've got a strong stomach, but there's so much I can watch before I pause the video and close the tab.
It makes no sense to me, the idea that there is an intelligent being who would design a world where peace was the operating principle, then turn it into a ghastly mirror image of itself for any reason. The idea that this being is the personification of love and kindness, yet would condemn the world to thousands of years of such unnecessary pain and horror and suffering is not logical or reasonable.
This being is so sensitive, that we are told He is aware of the passing of a small bird. So he must be watching when a crocodile grabs a water buffalo's leg and wrenches it hard enough to break it, then drags the horrified beast into the water to drown it, before tearing it to shreds and consuming it. Over and over and over, scenes like this happen all around the world. Day after day, year after year, for thousands of years. And this being watches it all. I am glad that I realized this only after coming to the conclusion that such a being doesn't exist.