There was a time in his youth that Moses was held in high esteem. He had a stellar reputation and was respected in the halls of government. He moved with prestige among the wealthy and was one of the most famous men of his time. By the time God spoke to him out of the burning bush (see Exodus 3:5), though, Moses had hit bottom and had faded into obscurity.
God couldn't use him until he tore Moses away from his worldly attachments. Who knew Moses now? Hidden away, out of sight, silenced and without influence, he had no outlet for his great energy.