The author of Hebrews says, therefore he had to be made like his brethren in all things so that he might become a merciful and faithful high priest. You might also say in another version, a compassionate high priest. And really, unless Jesus Christ were 100% God and man, that would never be possible. He had to be 100% man in order to sympathize with us, in order to empathize with us as humans. If he wasn't 100% man, then we just say, well that's his God talking, and he can never sympathize with us.
So The author of Hebrews makes it very clear that he had to be made like his brethren so that he can empathize with us, so that he can sympathize with us. Thank you.