A leader of a modern country with tens of millions of citizens or more has to be a bit of a jack of all trades but expert of none (or perhaps an expert of a small number of specialties). Most modern countries' governments are explicitly set up so as to have people lead branches of the executive who are (a) experts in a certain topic and (b) have the same political leanings as does the leader of the country. In Russia, these people are called deputy prime ministers. In Great Britain, they're called cabinet ministers. In the US, they're called secretaries, directors, or some other title. (The US Secretary of Defense is not the kind of secretary that you might ask to fetch you a cup of coffee.)
The concept is the same; it's only the titles that differ. The leader of a modern large country cannot possibly do the entire job of keeping that country going, and the leader will inevitably want those top expert positions to be filled with people who know what they're doing and who agree (more or less) with the leader of the country. In Russia, these key positions are informally categorized as Deputy Prime Ministers.