Appears all of the ministers have also resigned. I don't know jack about Russian politics so I'm unsure whether Medvedev resigning triggers all of this or if there is more to it:
https://www.thedailybeast.com/russian-prime-minister-submits-resignation-to-putin-reports-sayThe entire Russian government has resigned just hours after President Vladimir Putin proposed sweeping changes to the country's constitution, according to reports. The TASS news agency, which is owned by the Russian government, reported Wednesday morning that Prime Minister Dmitry Medvedev and his ministers submitted their resignations to Putin. The agency said Putin thanked Medvedev for his work and said the outgoing prime minister would be installed as deputy of the presidential security council. Medvedev said he resigned to give Putin space to carry out the changes he wants to make to the constitution. Earlier, Putin proposed changes that would limit the power of his successor if he steps down in 2024. That has been interpreted as a hint that Putin intends to take on a strengthened role as Russia’s prime minister or in the government’s state council. Under the current constitution, Putin should step down as president in 2024 after serving two terms back-to-back.
