“Why DOES HaShem have so many names?”
God had many names, and appeared in many forms even in the Old Testament. So your own argument, if it were valid, would invalidate your own Scriptures.
Fortunately, your argument is not valid. God is not limited by your lack of understanding, He can appear as He wills, in as many forms as He wishes, and remains the one true God.
Makes a Prot wonder about Rome's Mary and her many titles.