Lobster Mushroom is explained here:

"A lobster mushroom is made when the parasite Hypomyces lactifluorum invades wild fungi, namely the lactarius and russula mushrooms. These mushrooms are found in the fall, mainly in New England and in the northern areas of the West Coast. The parasite coats the wild mushrooms and turns them red, firming the flesh and giving the fungi a hearty meatiness that otherwise wasn't there. The lumpy-shaped mushrooms also take on notes of shellfish, namely lobster, especially when cooked.

It's because of the taste of the mushroom, the texture, and the bright orange-red color that lend the lobster mushroom its name. There are white lobster mushrooms as well, though these aren't as common as the warm-hued variety. The white lobster mushrooms taste similar to the red ones, but don't look like chunks of lobster meat and tend to have a lighter texture. "

https://www.thespruceeats.com/what-are-lobster-mushrooms-5190483)