Why Yeshua was called a Rabbi? He studied the Hebrew alphabet from a very young age. At 14th, he studied the Torah and by the time of 12, he memorized it all as he showed when he made his presentation at the Temple for his bar-mitzvah.
Yeshua studied like a rabbi, reading also the Mishna and Talmud. At age 30, he started his ministry and followed only the Torah. By this time he became a rabbi. It is important to notice that his ministry started at age 30 and lasted at least 10 years or so.
“I baptize with water, but there stands One among you whom you do not know.It is He who, coming after me, [i]is preferred before me, whose sandal strap I am not worthy to loose.”