There really are a lot of factors that I can think of. One of them is the publicity which depends on the strategies of the developers in making their altcoin or products sell to investors. Another would be how the developing team engages with partners, communicating with the community, and so much more. And of course, the concept of the project that the altcoin is for also matters a lot on how people need it or how big and how many problems it can solve. And then there's the bitcoin price which clearly drives the whole market either up or down. Now on some cases, economic factors really can affect the whole market depending on what is happening.