Why do they wrap them in wax and linen?

Answer 1

To prevent them from rotting and and to prevent them from melting while they are inside earth if you mean mummies.:)

Answer 2

Wrapping items in wax and linen can provide protection against moisture, dust, and pests. The wax creates a barrier that prevents moisture from seeping in, which helps preserve the item. The linen wrapping adds an additional layer of physical protection to prevent scratching or damage.