Well for the same reason that the ex-colonies were unhappy being ruled by Spain they were also unhappy being ruled by some centralised government elsewhere in Latin America. Bolivar had dreams of a Gran Colombia near the end of his life, but no one else was interested. Venezuelans didn't think Peruvians should have a say in their affairs and vice-versa. I don't know exactly what you mean by "went wrong", but I hope the answer that nobody was interested in what he was selling gives you the right idea.

Edit: I should expand, people respected Bolivar so they went along with his dream of Gran Colombia at least officially, but when he left that lip service went out the window. By the time he died no one was going to continue something that they only did cause he forced it on them.