I don't think that a former president of a particular country saying so again makes any difference. Besides, what real justification has he given to say that bitcoin is a ponzi scheme? There is absolutely no central entity in bitcoin since its goal is for decentralization, and there is utility value for bitcoin as it can be used as a store of value, and a means of transacting.
I wonder why the argument that is so easy to disprove is being used over and over. A ponzi scheme needs to be made by a person or a group that later takes money from new investors. Who would that person or group be in Bitcoin? It doesn't exist! If he knows it and still keeps repeating it like a parrot, it doesn't speak well about his intelligence.
Smart people don't make up stories and stick to them no matter what.
It's the same with any art piece. For one person it will be worth $1 and another will price it at $100. Many famous paintings that are now being sold for millions were once worth only a few dollars.