Everyone will get old, and white beard is no exception. Although he is the strongest in the world, after all, at the age of 70, his body organs will fail, his movements will get worse and worse, and his physical strength will inevitably decline. If you are sick, you naturally need treatment. Now many old people are also like this. They treat some diseases by infusion.
White beard's physical condition, as Kyle said, if he was the closest person before, it would be impossible to assassinate him, but now he is in poor physical condition, so he will be stabbed by Scuya.
But ODA sets this for a purpose ~
As we all know, White Beard defeated Red Dog at the top of the list, so obviously, if White Beard is in good health, Red Dog will be completely abused, and the strength gap between the General and the Four Emperors is too obvious, so Ota balanced the strength of the two.
In a word, white beard is the strongest man in the world. Although he is ill, he is still amazing at the top of the war ~