Question about drops (specifically legendary drops)

Is there any rhyme or reason for the drops? I'm trying to get a firewerks drop from splashzone. I'm on attempt 250 now with no drop to show for it.

For context, I'm level 50 and wanted an upgraded one from back when I was in my 40's.

Does me wearing a firewerks affect my inability to acquire one? Are there any other factors why I might not be able to get one?

Anyways, I'll be beating my head against the wall for a bit longer if anyone was wondering...