I don't think a lot of people supported demonitization as such - they supported action against black money and the government initially misled people into believing that demonetization would really work against black money. As far as mixing religion with politics is concerned, I don't think any political party can claim to be holier than thou in this case - they all incorporate caste, religion or region into their policies.
As far as your wish that Bitcoin was legal tender at that time is concerned, I don't think Bitcoin is legal tender anywhere in this world. Legal tender is of limited relevance in any case - it only means that you can use it to officially retire debts.
Many people supported demonetization but just before the cameras as if they don't support that, it would make them look guilty. In my place, all Gujaratis were supporting BJP and then when notes got banned, they gave up. They were the ones buying 500-1000 notes at 50% discount and Ebay was filled with orders. Now again I can see the same people supporting him and hence dissing cryptos. I am sure most of them would have converted their cash into cryptos but now most are left stranded as RBI has restricted it. Now things have become so bad that riots are taking place during elections and all this is because of both the parties.
Due to BJP offering subsidy and medicines at half price, people are supporting him but yeh sab moh maya hai.