why would you promise someone the stars and then all of a sudden change your mind?

i had been talking to a guy for a year. like any others.. we had our ups and downs.. when he was with his friends he never acted like he did when he wasnt with them. i totally always acted the same around everyone.

last week he told me that he wanted to always be with me and he wanted me to eventually be his wife.

so on wednesday we talked over the phone.. and he started saying well why do you always make it seem like things are my fault. you hurt me and you know what we'll just be friends like you say. i probably told him that once because it wasnt really official.

he knows how much i loved him back i always treated him like the king of my heart. as i said we did have ups and downs but more ups than downs. and then on wednesday he said "im hanging with my buds and meeting new people"
is he stupid?? why in the world lead someone on and then just say oh well.. we'll just be friends. i would always let him know how much i loved him.

my question is.. why in the world for one whole year.. would you promise someone the stars and love them and then all of a sudden out of no where would you say.. im meeting new people and lets be friends???