1. Theory. Shanks is a celestial dragon/he met with Gorosei that's why they stopped.
This is a theory not canon. A simple explanation is that Shanks is just the most reasonable of the Yonko hence why he allowed a seat at reverie.
2. The marines would have won because they have multiple people as strong as shanks
This is the 2nd argument used, its completely circular. The marines would have won because admirals and Yonko are equals. That's an argument people unironically use.
Its nonsense. Why? Because the war ended on Shanks terms. He challenged the entirety of marineford to a fight. They backed down. It was pretty clear from reading in a non powerscaling way Shanks had a good shot at winning.
This is a theory not canon. A simple explanation is that Shanks is just the most reasonable of the Yonko hence why he allowed a seat at reverie.
2. The marines would have won because they have multiple people as strong as shanks
This is the 2nd argument used, its completely circular. The marines would have won because admirals and Yonko are equals. That's an argument people unironically use.
Its nonsense. Why? Because the war ended on Shanks terms. He challenged the entirety of marineford to a fight. They backed down. It was pretty clear from reading in a non powerscaling way Shanks had a good shot at winning.