You must have come across the term 'pump and dump' schemes. Pump and dump happen when a group of investors buys an asset and pumps it to gain huge profits. It is usually followed by a dump (price fall). This would have a great impact on the market. There are groups of investors who would buy cheap altcoins at a lower price.

They will make people believe that it would eventually increase its value. Seeing this, many investors would invest in the asset only to realize that it would lose its value. New traders would be interested in investing in assets that bring them huge profits. So, they can fall prey to pump and dump schemes.