Generators go on the 17th floor so they can vent out exhaust and heat. Pumps need to go in the basement because you can only suck a liquid up by one atmosphere, which is something like 30' for diesel, but you can push a liquid up basically as high as you want. (Also, stating the obvious, the diesel tanker trucks are gonna be street-level, so you'd need pumps there anyway if you put the actual tanks higher.) This does, are you're pointing out, kinda stink if the pump itself is flooded, but the design's common and does make sense

Probably on the 17th floor to put the generators closer to the loads and reduce transmission losses. Also reduces street level air and noise emissions (and avoids street level air intake)

With fuel storage on the same floor for a reasonable runtime, larger fuel storage in the basement and a pump (or two) to move fuel, you're well prepared for lots of things. As long as the fuel throughput on the stairs is better than the fuel use rate, then you're ok for as long as you've got people to move it. Which is ok for exceptional incidents.

More than likely that's where the available space was. Data centers many large generators and there may not always be space in the lower levels to fit them, especially if the data center was not one of the original tenants.

Ground floor risks flood damage presumably? But this doesn’t explain why the 17th was chosen.

You put them up there so you get a voltage boost from the gravity pushing the electricity down. Put the generators on the ground floor, and by the time the electricity reached the top, there would be a voltage drop.