I don't see any evidence that it was ever a common expression before the cartoon.

Minced oaths generally date back much further than the 1800s. Socrates and Aristophanes give us examples in ancient Greek, and several slurrings of oaths exist in English from the early modern period on.

They exist today too in people saying "gosh" and so on, along with a variation for lavatorial and sexual expletives (sugar for shit, fricken for fucking and so on). They tend to be often localised in form, with for example jaysus for Jesus only appearing in and around Dublin, Ireland (a pronunciation that would once have been used only in some Dublin accents being adapted by other Dubliners exclusively for non-religious senses) and various expressions coming in and out of favour as with local slang expressions one finds varying greatly around the world.

Because of the great variety in real use, and the added requirement for such uses in some media (where the writer is not allowed to have Sylvester the Cat say "God-damn that fucking mouse!"), and the fact that most writers are writers and writers like playing with words, minced oaths have a greater variety in fiction than in real life (though life often imitates art in this regard). Holy Inventive Phrasing, Batman!

As such, "suffering succotash" was likely used precisely because it wasn't very likely to be heard as an actual minced oath and that, combined with the chiming of /sʌ/ in both words, and so is humorous. Indeed, in this case it would not so much be a matter of the cat's swearing being replaced by a minced oath as with the naff of "Porridge" and the smeg of "Red Dwarf" (where we could expect expletives to be a larger part of the characters' vocabulary if allowed) but rather he uses funny minced oaths purely because they are funny.