the quick answer is that it is actually rare for a fungus to attack a living plant unless there is some other kind of damage going on. not 100% as some can be problems, but most are harmless and are the kinds that feed on and digest dead plant materials or are symbionts or cohabitants.
Sounds like you may be talking about the mold that causes damping off or maybe similar molds. Molds are a member of the fungi family.Thanks,
I believe you're right but also, there are some fungus which are known to be soil fungus and lives in soil, they can penetrate the plant and decompose the living tissue while plant was taking nutrient from the soil and they get the plant weaken and wilted because the plant won't be able to take enough nutrient after getting weaken and it ends in nutrient deficiency that will cause ut to become wilted and die.