yeah, in stead we polluted the gas giant's presently unknown about biosphere with our invasive organisms, not to mention nuclear fuel.
1: I know this is a joke, but I'm going to
tear it apart with science anyway.
2: There's no way in heck anything from Cassini could survive in Saturn's atmosphere, between the super cold temperatures, sanitizingly hot reentry, And also buoyancy. Saturn is made mostly up of hydrogen and helium, not only that, Saturn is the LEAST DENSE of the gas giants, making the problem of staying aloft even harder, even the lightest of Terran tardigrades, microbes, viroids, or even just naked RNA strands would either sink straight to Saturn's core, or in the latter two cases; get transformed via Photodissociation into Petrochemicals.
Heck, I would hypothesize that; due to Saturn's low density, metallicity, and temperatures, if lifeforms adapted for gas giants exist, Saturn may be ill suited for them. but I could be wrong on that.
3: I'm fairly certain Saturn is
WAY more radioactive then Cassini, and yes, it's magnetosphere is oddly weak, but Saturn's surface area is roughly 4.27×10
10 km
2 (1.65×10
10 sq mi) a little bit of nuclear fuel aint'gonna do. . . anything.
4: Cassini did not have the Delta-V needed to leave the Saturn system, with minimizing possible contamination in mind, can you tell me what better options there were for things to crash it into?
(aside from the Carthage) 5:
I KNOW YOU WERE JOKING, I JUST WANTED TO SHOW HOW BIG OF A SPACE NERD I AM. 
Ahem, with that out of the way, here's more awesome science for ya me hardies.
