It’s a fantasy world with superhumans. Brownbeard, Usopp and Nami-in-Sanji’s body all survived an explosion as big as Pedro’s, and Brownbeard and Usopp certainly aren’t as strong as him- Sanji’s body could well have been tougher, although with Nami in it it wouldn’t have been able to use CoA. Look at the size of that explosion compared to the size of the ship that can hold giant sized children quite easily. About the same as the Pedro blast
The blast could have killed Pedro, it could also not have. There’s no hard and fast rule here. Luffy can cause more damage with a punch than that explosion, but he doesn’t leave a trail of dead bodies in his wake.
I tend to think he’s alive because Perospero could survive it, Pekom’s story with Pedro being the only one capable of calming him down never really got concluded and it’s OP where death is rare. But then Oda did kill off Yasu- much more explicitl- with it being compared directly to Pedro. That could well mean Oda’s started killing to reflect the serious endgame stage of the story we’re at. We won’t know for certain until Pekoms shows up again, I think.