I find ironic that the worst champions in normals. . .
get to be actually strong in special game modes or ARAM

anybody mind explaining why this happens?
get to be actually strong in special game modes or ARAM

anybody mind explaining why this happens?
Because the entire reason they're bad on normal SR is because of the way their kit functions. They end up too strong or too weak. In special game modes, you get to bypass laning, or at least their laning weaknesses, making them (usually) strong. Not to mention most of them either have too much damage, too much mobility, or too much utility when they're strong, and its much easier to accomplish their 'fantasies' in special game modes, especially URF because their kit's DPS, utility, or mobility is magnified x5.
Also, you forgot
all being good in URF, if played properly.
"worst champions"
3/4 the champions you listed are good or at least viable m8
actually all those champions are strong in normal games if played correctly and built right.

Because URF turns slower ability-based DPS into terrifying Ultra Rapid-Fire carnage. All the champs with somewhat weaker but very short spell rotations suddenly become amazing.
I've been dumped upon, and i have dumped on people with all the champs in normals.
Kass was used in lcs often as well as urgot once fiddle is just hidden op Jayce high mana costs good damage though Shaco is good if you know how to use him yorick also hidden op