The market cap of a cryptocurrency can rise pretty fast after it is launched and this is a result of many things including; anticipation, marketing, speculative interest, and most importantly the community of users. In cases where a token starts trending, a lot of buyers are able to come on board very fast and this basically pushes up the prices and the market cap within a short time. Also, growth may be enhanced by locked liquidity in the token along with a certain use case or theme which applies to the crypto world. But this improvement is usually unstable and quite unreliable.