Because holy sh!t that's a lot of water.

(apologies in advance)
Getting out the submersible pump, again.
I’ll answer you question with a question.
What the heck is holy sh!t?It's a well known expression (most often in response to surprise or amazement, good or bad).
I was not intending irreverent offense to anyone, just amazement in how much water falls in so short a time. Gutters, roof, sump pump roaring, back yard yachting. For some 26 years it was very rare. Now it's all the time.
I'm getting more efficient in pumping out the yard, everything lined up ready to go. Quick hookup, and about 3-4 hours constant run to the storm drain. Never happy playing with electricity and water, so I plug in last from safety.