Hello there!

They excrete chemical compounds called "exo-enzymes" that quite literally digest the medium around them.

Those exo-enzymes depend on the species of fungi. Also, the ground is already inhabited by lots and lots of fungi, and that leads to competition between them. They adapt to their environment, and if there were only hyphae and no ground left it would become a literal war. Survival of the fittest, sort of. Some would evolve traits that allowed them to consume other, weak species of fungi.

Thanks for listening to my TED talk!