Because they are non renewable sources of energy and they took billions of years to form.
Cohesion: When water molecules stick to one another through cohesion, they fill the column in the xylem and act as a huge single molecule of water (like water in a straw). Capillary action: Capillary action is the movement of a liquid across the surface of a solid caused by adhesion between the two.
They are eukaryotic and don't move, plants are autotrophic - making their own energy - and have cell walls made of cellulose, but fungi are heterotrophic - taking in food for energy - and have cell walls made of chitin.
They may have ran out of oxygen, or they may not have been water dwelling snails, as not all are, lack of food, no flow of water into and out of the tank would cause them to run out of oxygen.
You weigh less if you’re on the moon