From :

Since then, reports have floated around online that Miller and star/producer Ryan Reynolds disagreed about the scope of the sequel. Deadpool was famously made on a modest budget, and some questionable reports suggested that Miller envisioned the sequel as a much bigger-budget affair. But during a wide-ranging interview on CG Garage, Miller finally spoke out about why he left the project and he made it very clear that was never the case.

Read the Full Story