Simplify the following text for a Grade 11 native English-speaking person.
Original: However , saturation of the market in 2009 by numerous spin-offs from the core titles led to a nearly 50 % drop in revenue for music game published , causing them to scale-back plans for further expansion in 2010 .
Simplified: However , because there were so many spin-offs from the core titles in 2009 , there was a nearly 50 % drop in sales for music games , causing them to scale-back plans for further expansion in 2010 .