Which factors helped rebels topple Syria govt in 13 days after failing for 13 years?

Ousted Syrian President Bashar al-Assad's allies Russia and Iran being busy in wars likely helped rebels in toppling Assad's rule in 13 days despite failing for 13 years. Rebels reportedly also received help from Turkey as Assad's ouster may encourage refugees in Turkey to return. Israel's attacks on Iran-backed Hezbollah and on Syrian weaponry may have further weakened Assad's government.