From observation, the movement of alt coints on exchanges or during an ICO don't really reflect the inherent value - they reflect the level of hype.

People or groups expect a coin to do well, or they expect that enough other people expect it - so they buy.

Some fractional subset are sincere in their beliefs that it's the Next Big THing. A larger group of buyers are convinced by the passion of the original group. But the majority pile on because they expect to make short- to medium-term profit on price fluctuation.

Very similar to the stock market.