When Nat first started The Novel, she unintentionally wrote it in third person omniscient. She thought this an excellent way to write and thought it not jarring at all to switch between the heads of her characters at completely random intervals. It was also written with many passive sentences that made sentences a lot longer than they needed to be. Her husband thought it odd that she'd write a book at all, because only nerds did that, and he certainly hadn't married a nerd.
Then Nat submitted The Novel to its very first critique group. How shocked she was to learn she'd forgotten everything from English class and that her random head-swapping drove her readers crazy! But she could fix it; she rewrote every word and hacked off every funky adverb, and characters no longer said things merrily or blurted them out or sighed them, but just said them, and how they said them said everything. She limited her head-swapping to natural breaks in different chapters and thought now, she really had something.
Her husband decided he could live with that.
Soon after, Nat submitted The Novel to its very first editor. Where she realized that despite how clean the breaks were between characters, switching to another character's point of view for just a few paragraphs, to tell a tiny piece of the story, wasn't really... standard. Nor was it any new genius way of writing. She had a choice to make: minimize the number of viewpoints and write more of the story outside the MC, or change the entire thing to third limited.
She thought of books she loved, like Harry Potter and A Monster Calls. She thought of how disconnected she felt when more than two narrators told the story, and how she really preferred one.
She rewrote every word, again, from just the MC's point of view.
Then a few months ago, I started thinking about some amazing books I'd read in first person present tense. How immediate they felt. How I connected so much faster to the main character. How every thought just happened, and it wasn't forced, and for Pete's sake I teared up when a fictional dog died and I knew I had to have that. I don't know if I've succeeded, because a lot of the power behind first person is simply being human, thinking the good things and the bad things and everything between. I want to believe I've done a good job, but months pass and the publishing world gets bigger and I don't know anymore.
But that's what I've got so that's what I'm going with.
And that's how The Novel made it to first person.