People pretend Bajrang Gun doesn't matter to an explosion destroying a mountain range mainly because of Bajrang Gun's size but y'all fail to realise that we're talking about an ISLAND SIZED PUNCH; it releases loooots of kinetic energy to only make such large amount of mass move. Luffy was straight up punching Kaido with speed as if he's punching normally. It's totally different and if it hit Wano, it would create even more damage than the panels below, which I'll post now:
This is what Bajrang Gun managed to do without touching the country:
It created a hole which is essentially the same size of this one:
(Ignore the pixelscaling, it's just about the image)
So again, Juubi was destroying more mountains on screen but it didn't puncture a whole ass hole which goes to the lava chambers of the country.
Plus, the mountains on Wano are gigantic large. Some were even comparable to Zunesha iirc.
Even if we disregard all of that, Sickbeard moved tectonic plates and his earthquakes reached islands several hundreds of miles away from MF. Kaido is significantly stronger than that WB.
Bruh what?
There's a mountain RANGE on top of the skull... The very same rooftop kept more than enough space for a mountain sized dragon to wreck havoc on this, lol.
Forget the outer layer of even larger mountains surrounding this island.