Some people may commit robberies and murders because of jealousy,greed and hate ^ I guess

Yes, ''greed'' is a noun whereas ''greedy'' is adjective and ''because of'' is mostly followed by nouns plus you aren't describing something or someone after these words, so it is not an adjective.

Yes, you're right. Greed is the noun and greedy is the adjective. Here, you need the noun. Hope this helped :)