The phrase "a lot of publishers" means that there is a large number or variety of companies that produce and distribute books, magazines, newspapers, and other printed materials. Full definition
Likewise, there are lots of publishers out there who only publish certain genres (children's, educational, spiritual, etc.). (wiseinkblog.com)
Customers might be happier if lots of publishers sign up for a 20 % discount rather than have just a few sign up for a 50 % one. (thefutureofpublishing.com)
This table from comScore shows March was a strong month for lots of publishers. (businessinsider.com)