People answering polls have pretty varying views of what "Sharia" means, since that name tends to be used by any system of law that claims to be based on Islam. If you ask more specific questions, like whether a rigid Saudi Arabian / Wahhabist style interpretation of Sharia should be introduced in their country, support is much lower, though it depends on the country. One example: 60% of Malaysian Muslims believe that their country's current legal system is sharia, so when they say they support sharia, they mean the system Malaysia currently has, rather than a Saudi-Arabia or Taliban or ISIS style system.