Here's why:

* Granite is an igneous rock. Igneous rocks are formed from the cooling and solidification of magma (molten rock beneath the Earth's surface) or lava (magma that has erupted onto the surface).

* Intrusive igneous rocks like granite are formed when magma cools and solidifies *within* the Earth's crust. This slow cooling process allows for the formation of large mineral crystals, giving granite its characteristic coarse-grained texture.

So, granite is indeed made from magma that was trapped in the crust.