As earthworms crawl in through tightly packed soil, they break it apart, making it more porous.why would this?

Question

As earthworms crawl in through tightly packed soil, they break it apart, making it more porous.why would this?

Answer 1

... help agriculture? (guessing the end of your question)

Because this helps the passage of water and air through the soil, aiding both plant growth and the growth of microorganisms in the soil. (In fact, earthworms only play part of the role in breaking down soil - bacteria,  and other microorganisms are much more important in converting organic matter to nutrients available for plant growth (particularly nitrogen).

Earthworms also digerst organic matter in the soil, and excrete friable material ('worm casts') which aid in making the soil more granular.