Why do some mushroom species glow in the dark?

The exact reason is not completely known however the leading theory is to attract insects to help spread spores. Not all mushrooms light up in the same spot and even mycosal networks underground can sometimes light up. Often luminous mushrooms tend to grow where there is little wind, insects are an excellent way to spread the spores to new places. While it seems most mushrooms will only glow at night, others under good nutrition conditions will continually glow. Nature always finds a way! One other theory was that they would glow to make insects and arachnids that eat the mushroom more visible to preditors and thus protect the mushroom.

https://www.forbes.com/sites/linhanhcat/2019/10/08/mushrooms-glow-in-the-dark/?sh=38abfc474e70

Bioluminescence is light generated from chemical reactions in the bodies of living things, and beings from fireflies and jellyfish to some bacteria and – yes – fungi can produce this effect. Bioluminescent reactions in fungi follow a basic formula: an enzyme interacts with a light-emitting compound with help from additional enzymes, water, and oxygen. The light-emitting molecules are called luciferins, and the enzymes that interact with them are called luciferases. All 120 known bioluminescent mushrooms use the same family of fungal luciferins and luciferases.

https://northernwoodlands.org/outside_story/article/bioluminescent-mushrooms