It's possible to pump the market to almost any size if there way to organize a huge community push to do. However, the cryptocurrency community is highly dispersed and there is very little in the way of organization, except for a few small pump and dump groups, though even these tend to only have the power to pump trash coins with almost zero volume.
Yes it is possible but only the big whales can do it, the problem is how can we find the genuine groups how can we trust them. Even i joined some groups and followed their signals but lost my money. So be care full before following any pump groups.