Why did Satan choose a snake to deceive Eve?

The Bible doesn’t indicate why the enemy chose to use the body of a snake to deceive Woman. We must presume that there was nothing inherently special about the snake before Satan chose to indwell it. Once he entered the snake, then the Lord memorialized the snake’s role by altering its appearance forever:

Gen. 3:14  The Lord God said to the serpent, “Because you have done this, Cursed are you more than all cattle, And more than every beast of the field; On your belly you will go, And dust you will eat All the days of your life;
 

You may find our Genesis Bible Study helpful.