India didn't ban cash. They took 500 and 1000 rupee notes out of circulation, and replaced with new notes. This was 86% of call cash in circulation. The goal was to get all the "hidden and underground" cash out on the table, and force hoarders and the underground to come clean.
They hoped by this process to also promote increased reliance on digital currency.
But it was NOT forcing the population to 100% digital currency.