I guess question is less of was it successful but rather was it necessary and did the move do any good at all?

One thing I can't understand is, when I look up all the countries/regimes/dictators in history that have tried demonetization, and almost always it was done for the same reason - curbing corruption, black money, counterfeiting etc., and generally it resulted in people losing confidence in the institutions/governments, no real dent in corruption, counterfeiting even decades later. Unless I missed something, it just puzzles me why we would try it now and expect a different result.

What all countries/regimes/dictators have tried this? And what has been their results? I surely would like some source to back up what you said.

Basically the Indian government hoped that any "hoarded" undeclared (not taxed) notes would suddenly become worthless, and therefore not be deposited. Instead, almost all notes in circulation were deposited, meaning any undeclared currency managed to be declared in time.

"I am confused with the article though. What would have been a successful result? That the all canceled currencies wouldn't have been exchanged or deposited?"

Yes - exactly - the assumption earlier was that a significant amount of money stored with the denominations that were de-monetised was "black"/unaccounted money. And this would not be deposited into banks due to fear of being scrutinized. If this had happened on a large scale and if the money had not been deposited - the liability of the exchequer would have reduced.

That is assuming the whole stuff was done for the singular goal in mind. There could have been multiple reasons: a. End counterfeit money b. Make a list of hoarders as everyone depositing money needed to show identification.

It is going to be interesting times ahead with the data they might have collected.