The reasons for this decision are still unknown.

President of Ukraine Volodymyr Zelenskyy removed the head of the Office of the Prosecutor General, Irina Venediktova, and removed the head of the Security Service of Ukraine, Ivan Bakanov, from his duties.
The corresponding decrees appeared on the website of the Office of the President.
“In accordance with the second part of Article 11 of the Law of Ukraine “On the Legal Regime of Martial Law”, I decide: to remove VENEDIKTOVA Irina Valentinovna from the post of Prosecutor General,” the message says.
By another decree and Zelensky appointed Oleksiy Yuryevich Symonenko as Prosecutor General.
“In accordance with Article 47 of the Disciplinary Charter of the Armed Forces of Ukraine, approved by the Law of Ukraine dated March 24, 1999 No. 551-XIV, remove BAKANOV Ivan Gennadyevich from the duties of chairman of the Security Service of Ukraine,” another message says.
Earlier, the president reacted harshly to the reports of the mayor of Ivano-Frankivsk, Ruslan Martsinkiv, that the Russian Federation could launch a massive missile attack on Ukraine. Zelensky urged Ukrainians to be careful and prudent in the information field and not to believe in the “throw-in” of the Russian Federation.
(C)UNIAN 2022

Don’t feel any pity for this bitch, she had a personal vendetta against Poro.
Oh shit!! May not disagree but in the middle of a war. I don’t know if it’s that smart or just hire a strong deputy and put them on the sidelines. IMHO
The head of the SBU was also fired. I believe it’s something to do with collaborators.