This. It got that big by eating the wildlife that is supposed to be there.
These are people's escaped pets. Not only are they fucking up the ecosystem, they are cross breeding with other snakes and creating aggressive hybrids.
Burmese pythons are highly invasive to Floridian ecosystems. Back in the day, a lot of idiots would purchase them as pets without realizing how big they would get. Instead of handling it responsibly, the owners would let the pythons out into the wild when they grew too big. It sucks, but taking them out is the only reasonable way to deal with such an issue. Similar situation with wild boars, except those guys are tasty.
You're partially correct in that they are invasive and destroying the ecosystem of the Everglades. However the outbreak can be traced back to a reptile center that was destroyed during hurricane Andrew, not necessarily people releasing their old pets.
From Wikipedia:
Although the exact origin of Burmese pythons in the Everglades is unknown, it is likely that many were once pets released by owners who found them too difficult to care for.[8] However, the majority of experts concur that the python population grew particularly after Hurricane Andrew. The category 5 storm destroyed a python breeding facility, which released numerous snakes into the adjacent swamps.