The future is not set in stone.
He heard those lines before, spoken of his concerns of choice. But everyone, even the Tower felt it wasn't the answer. But really it was two things that truly convinced him. Seeing that future version of Peter, hardened and cold, as though his spirit was burned away with half of the city when he exploded.
And Claire, his lost daughter. That look on her face, so determined, like his own eyes at times. Staring back with anger and disgust at him before she jumped out of the window. That was his family.
New York is his city. He can't abandon them. He ignored his mother's pleas as he walked away from the helicopter, and took the sky. Seeking out his brother, and then hearing his daughter screaming as she held a gun to Peter.
There is another way. I can help. Just trust me.
"You ready?"
I love you
The sky claimed them, and he thought they would burn together.
"You go, I go!"
But then he was pushed away and watched his brother spiral away.
And there was light, and fire reaching out.
And like a latter day Icarus, he fell. Falling into darkness.