Why was Jesus not a vegan?

Answer 1

because god gave animals to man to rule over (this includes eating).

Vegan is a fairly recent eating innovation. Jesus was a Jew two millenia ago and so followed Jewish dietary laws. As a Jew, he would be required to eat lamb on the Day of Atonement. Other times of the year, something approximating a vegan diet was probably possible. The cool winters in Judea would make a completely vegetable diet a challenge, but not necessarily impossible.

Typically, a vegan diet often is related to an ethical viewpoint that simply did not exist in the time of Christ. Animals were considered to be a source of food, a source of labor, a source of clothing, and a source of sacrifice. The vegan ethical model simply was foreign to Jewish and early Christian thinking, so a vegan diet would not be sought or valued.