You have to realise that support for Independence is not confined to members of the SNP although it is also worth noting that the SNP has the 2nd largest (after Labour) fully paid up membership in the UK, from a Scottish population of 5 million.
During the 2014 referendum a plethora of groups were set up under the YES umbrella - everything from Labour Members for Independence, through Grannies/ Rangers + Celtic supporters/NHS workers/Shepherds/ etc. etc for Independence. Some of these groups e.g. WFI (Women for Independence) and RIC (Radical Independence Campaign) and area based YES Groups, have remained active, not only campaigning but doing much good supporting foodbanks and other causes.
The Scottish Green Party is also firmly in favour of Independence and together with the SNP ensures a pro-Indy majority in the Scottish Parliament.
The impression given by the MSM i.e the BBC and all the Unionist Newspapers - (only the National is pro Independence) - is that support for Independence is low and everything the Scottish Government does is terrible but opinion polls show a different story with satisfaction with the Scottish Government, the Scottish Health Service, Education, ect. consistently showing higher satisfaction levels than those in the rest of the UK .
Recently statistics have shown that average wages in Scotland are higher than RUK, educational attainment likewise and NHS targets although set higher than those in E&W are more consistently met and so it goes on. Yet the public perception is that Scotland is too wee, too poor, too stupid to run its own affairs successfully, when the reality is that on most measures it is out performing the other nations and regions of the UK - and this with less than 1/3 of the powers devolved and under Scottish Control.