How Kösem Sultan really died - historical facts

How and for what reason was Valide Kösem Sultan executed? Was Turhan Sultan guilty of this? What history says.

[joannaflores]

But after the death of Kosem Sultana, Sultan Mehmed signed a treaty with Germany, and that's the start of the fall of the Ottman Empire. Turhan failed, not enough intelligence like Kosem and Hurrem, his son failed.