I just realized this: Whitebeard is smart, he knows what his Fruit does. I believe he also had some knowledge of the prophecies regarding the Dawn: he was so close to Roger, and Oden. Newgate had to have triggered at least volcano over the years with his earthquakes. Why on earth would he want to cause a volcanic eruption in his Nakama's Home Country? Kaido knew Whitebeard's Fruit from Rox days, and knew Newgate wouldn't be willing to risk the damage.
Newgate vs Kaido without his Fruit, I'm taking Kaido.
Kaido was the coward: he used Wano as a shield, so Newgate couldn't stop him.
We'll probably get some flashback to this when we see Kaido again and the Whitebeard Remnants/Roger Remnants sail to Wano: Gyaban already foreshadowed this happening.
We know earthquakes make Mt. Fuji explode from right after Luffy beat Kaido, when we cut to Bananuki-san in Udon Prison:
This is what Marco meant: if Newgate fought Kaido in Wano seriously, Mt. Fuji is fucking exploding, and killing a shit ton of people. To a country that was already on the verge of collapse, this could have been it.
Also Pluton/Dawn 20 Year Prophecy stuff
Newgate vs Kaido without his Fruit, I'm taking Kaido.
Kaido was the coward: he used Wano as a shield, so Newgate couldn't stop him.
We'll probably get some flashback to this when we see Kaido again and the Whitebeard Remnants/Roger Remnants sail to Wano: Gyaban already foreshadowed this happening.

We know earthquakes make Mt. Fuji explode from right after Luffy beat Kaido, when we cut to Bananuki-san in Udon Prison:


This is what Marco meant: if Newgate fought Kaido in Wano seriously, Mt. Fuji is fucking exploding, and killing a shit ton of people. To a country that was already on the verge of collapse, this could have been it.
Also Pluton/Dawn 20 Year Prophecy stuff