Mr. Wyler, an executive based in Boston who made his fortune during the tech boom, said he would lace Rwanda with fiber optic cables, connecting schools, government institutions and homes with low-cost, high-speed Internet service. Until that point, Mr. Wyler, 37, had never set foot in Africa — he was invited by a Rwandan government official he had met at a wedding. Mr. Wyler never expected to start a business there; he simply wanted to try to help the war-torn country. But after nearly four years, most of the benefits hailed by him and his company have failed to materialize, Rwandan officials say. “The bottom line is that he promised many things and didn’t deliver,” said Albert Butare, the country’s telecommunications minister.