This might sound ridiculous but there is a chance market cap isn't truly increasing.
What we may be seeing is a shift of market cap from fiat to crypto currencies. Crypto's rising market cap might better be described as a paradigm shift whereby wealth is shifting from traditional fiat currencies and the economies they represent.
Well, that is probably true, but what else should we expect? It is natural that there doesn't appear more money in general in the world. It is a good thing, because if it was otherwise there will be the devalvation, since the number of goods remains while the sums of money increase. Yet I think that with time some new services appear and in that case the amount of all the world money is naturally becoming bigger.
People turning from fiat to cryptocurrencies is pretty much what people want to happen, since this way coins will take the niches that belong to fiat now, so the world economy will eventually become decentralized.