Bull run is somehow manipulated by those investors and pumps. We all know that cryptocurrency is still very young that only few have known this. Now, bull run is one way to attract new investors and at the same time making the rich holders richer. The decentralized system of cryptocurrency makes the task for manipulators easier. There are.no rules and regulations and everything is anonimous. It's very hard to trace those manipulators and pumps.
Some coins will tend to have bull run, especially new listed coin they can easily make it pump, but those larger and established coins will be needing group of investors in different areas to make it notice a jump.