Why was a figure of speech used for the windows of heaven, but not for the fountains of the great deep?
Did someone say "fountains" wasn't a figure of speech?
Of course it is!
But a figure of speech means something.
"Fountains of the great deep" broke forth.
"The windows of heaven" were opened.
Doesn't it seem like the two would be treated the same, or if as you say, at least have connecting text to show that the literal one caused the figurative one
The "connecting text" is the "and."