# Therefore
"For that reason"
# his disaster will overtake him
This implies that the disaster is chasing him like a person or an animal, and that it will catch him soon. Alternate translation: "his disaster will catch him" (See: [[rc://en/ta/man/translate/figs-personification]])
# his disaster
This refers to the disaster that will happen to him, but also the disaster that he himself caused.
# in an instant; in a moment
Both mean the same thing, and one or both of them can be replaced by "suddenly" or "very quickly."