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. If the world's markets and economies are dwindling and growing less wealthy over time, that might be explained by the world's wealth being shifted into bitcoin instead.

What we may be seeing is bitcoin gaining value as people abandon the world's markets and fiat currencies and choose to pour their wealth into bitcoin/crypto, instead.