Why was early Earth extremely hot?

At its beginning, Earth was unrecognizable from its modern form. At first, it was extremely hot, to the point that the planet likely consisted almost entirely of molten magma. Over the course of a few hundred million years, the planet began to cool and oceans of liquid water formed. As the early Earth accreted around 4.5 billion years ago, it had a hot volcanic environment and a surface bombarded by asteroids. The earliest undisputed evidence of life on Earth dates at least from 3.5 billion years ago,