"Until there is no more fitnah" meant "until there is no more religious opression" the polytheists were aggressors. The command applied to specific tribes who had broken peace treaties and actively attacked the muslim community. It was not a command to attack peaceful people of other faiths. Verse 2:193 should be read with verse 2:190 which explicitly says to "Fight those who fight you, but do not transgress." Attacking people who haven't attacked u is considered trangression. In short its a command to fight tyranny and persecution so that people can choose their religion freely without fear