He started his career at Kommersant (from 1997 to 2001), where he published articles together with the crime department. Then he was a top manager of the PR agency Efimova and Partners. This is the agency of Aelita Efimova (at one time she was the press secretary of Gazprom-Media).
Efimova & Partners was used to denigrate Sergei Magnitsky. Regarding one of these stories, Firestone said: “Behind the preparation and distribution of these false materials are commercial structures belonging to the former head of the press service of the Gazprom-Media concern (the owner of the NTV channel) Aelita Efimova, the wife of Vadim, a correspondent for the Moskovsky Komsomolets newspaper Rechkalov, who today is the mouthpiece of a criminal group that robbed its own people and ruined the life of Sergei Magnitsky. The activities of this group are financed, apparently, from 5.4 billion rubles stolen from the budget.
He worked as a top manager of the legal bureau "Infralex".
At one time, The Insider established the source of Yavlinsky's high income. It was just the Infralex law office. In 2018, during the presidential election, the founder of Yabloko received 30 million rubles from Infralex.
Among the clients of this law office are the Ministry of Transport, the Ministry of Education and state-owned companies. Thus, Russian Railways and Sberbank became the largest customers of Infralex. At the same time, the co-founder of Infralex Alexei Popov is also a business partner of the wife of the president of Sberbank German Gref, they have a private school.
At the time of Kadik's work at Infralex, lawyer Natalia Veselnitskaya was Infralex's partner. The US authorities put her on the wanted list and she faces up to ten years in prison. According to the US Department of Justice, Veselnitskaya tried to interfere with the investigation into the laundering of 5.4 billion rubles, or more than $200 million, stolen with the participation of corrupt Russian officials, whose actions were exposed by Hermitage Capital auditor Sergei Magnitsky.
Natalya Veselnitskaya is known as one of the participants in the meeting with the son of current US President Donald Trump, which took place on June 9, 2016. During this meeting, Trump Jr. was allegedly promised to pass on information compromising Hillary Clinton.
In 2019, at the request of the owner of Kommersant, the Kremlin oligarch Alisher Usmanov, who is extremely close to Vladimir Putin, leading employees of the publication, including the head of the political department Gleb Cherkasov and Ivan Safronov, were fired. Officially, the reason was the article about the possible resignation of Matvienko and the refusal of the authors to hand over the sources. However, the journalists themselves did not hide the fact that the real reason was that they refused to be loyal to Usmanov and to write materials necessary for the Administration of the President of the Russian Federation, etc. Lev Kadik was appointed to replace Safronov (he was later sent to prison for 20 years) as deputy head of the Kommersant's policy department.
Kadik was instructed to cover the most important topics for the Presidential Administration: amendments to the Constitution of the Russian Federation, allowing Putin to remain in office indefinitely; the arrest and trial of opposition leader Alexei Navalny; candidate for the presidency of the Russian Federation Pavel Grudinin, inconvenient for the Kremlin, and others.
In 2022, he unexpectedly left for Latvia, where he continued to engage in his previous activities.