I post quotes below because some of the articles might be paywalled.
The Financial Times: The arrival of a Russian oligarch in the disputed enclave of Nagorno-Karabakh has added to escalating tensions in a volatile region where Moscow is struggling to maintain its influence. ... The oligarch was appointed as Nagorno-Karabakh's first minister by its president Arayik Harutyunyan last October. But analysts see his arrival as part of Moscow's attempt to reboot its regional leadership. ... Russian-Armenian Billionaire Ruben Vardanyan was appointed last autumn as first minister in the South Caucasus enclave, which is claimed by both Armenia and Azerbaijan, but his longstanding ties with the Moscow elite have aroused suspicions in both Yerevan and Baku.
Time magazine: Man from Moscow? But the standoff between the two sides has only worsened in recent weeks after an enigmatic Russian-Armenian oligarch, Ruben Vardanyan, announced he was moving to Nagorno-Karabakh in September. The Yerevan-born billionaire was initially coy about seeking political office but, two months later, was suddenly appointed State Minister of the unrecognized Republic of Artsakh, making him effectively the most powerful man in Stepanakert overnight. Since then, talks with Azerbaijan have broken down, with Aliyev accusing Vardanyan of having been “sent from Moscow with a very clear agenda.” Officials in Baku point to the fact that he has been sanctioned by Ukraine as proof of his close ties to the Russian state. Kyiv says his business interests “undermine or threaten the territorial integrity, sovereignty, and independence of Ukraine.”
Laurence Broers, one of top experts on South Caucasus, for Der Spiegel: The fact that this blockade is taking place now might have to do with the leadership change in Nagorno-Karabakh itself, in particular with Ruben Vardanyan taking office as minister of state of the de-facto republic in November. This Russian-Armenian businessman appears to be close to the power elite in Russia. In the fall, Vardanjan made a surprise announcement that he was giving up his Russian citizenship and moving to Nagorno-Karabakh. Many in Azerbaijan see him as a Russian puppet, someone who intends to advance the transformation of Nagorno-Karabakh into a Russian protectorate along the lines of South Ossetia and, in the longer term, possibly also challenge the current leadership in Armenia.
Eurasianet: And suspicions about Vardanyan’s agenda are fueled by the fact that he doesn’t have a natural political constituency in Armenia or Karabakh, Giragosian said. “Vardanyan has been out of Armenia since 1985, with no local power base and marginal political standing or status,” he said. “Despite his impressive philanthropy in Armenia, Vardanyan is still a product of Moscow, as the source of his wealth and as the center of his influence. And even his record as a Russian businessman is seriously tainted by his involvement in a criminal money laundering enterprise on behalf of Putin-affiliated interests and individuals.”
I addition, Vardanyan was questioned on BBC HARDtalk by Stephen Sackur about his connections to the Russian government, etc. Here's transcript: [1], video: [2], BBC news report: [3]
An article in Forbes magazine also discusses the role of Vardanyan in the crisis: [4]