The athlete’s foot fungus, tinea pedis, is a surface fungus and belongs to the family tinea which also include the tinea corporis. Tinea corporis is a surface fungus that causes crotch itch. In crotch itch, it does not “chew” into the flesh. Tinea pedis does penetrate and chew up the skin layer and expose raw flesh but it does not go inside the flesh.
Clostridia is a bacteria which causes gangrene. It goes inside the flesh when there already is an open wound and it creates blisters with foul pus in the flesh. That is why gangrene has an open sore that is deep enough to harbor pus-filled blisters.
In contrast, with athlete’s foot, the open wound with raw flesh exposed stays as an open surface wound with raw flesh exposed.
It is the invasion of the clostridia into the already open sore of the athlete’s foot that causes deterioration of athlete’s foot wounds to become something more than just an open flesh wound that exposes raw flesh.