Why have so few Muslim leaders publicly condemned radical Islam.?

It's no different from Christian leaders who fail to publicly condemn radical Christianity. Sensible people realize that it is not the responsibility of every religious leader to lend more credence to the radical elements within their religion by giving such elements the acknowledgment they desire through public condemnations. Sensible people realize that such groups are extreme and do not reflect the majority of any religion. Those who wish to state otherwise are bigots.