Combination of recurring pro-Kremlin disinformation narratives about the downing of flight MH17, including a longstanding pro-Kremlin disinformation narrative about Ukraine's Euromaidan protests, as well as painting the West as the puppet-master of Ukrainian politics and portraying Ukraine as an anti-Russian project.
The JIT has provided concrete evidence of Russia's involvement in the MH17 shot down. On the 28th of September 2016, the JIT announced that flight MH17 was shot down by a missile from the 9M38 series, which was launched by a BUK TELAR missile system. The system was transported from the Russian Federation to an agricultural field near the town of Pervomaiskyi in Eastern Ukraine, where the missile was launched. After firing, the BUK TELAR was transported back to the Russian Federation (with one missing missile). On the 24th of May 2018, the JIT announced that the BUK TELAR came from the 53rd Anti-Aircraft Missile Brigade, a unit of the Russian armed forces from Kursk in the Russian Federation. On the basis of the JIT’s conclusions, the Netherlands and Australia are convinced that Russia is responsible for the deployment of the BUK installation - both governments are formally holding Russia accountable. The JIT conclusions were further corroborated by the Bellingcat Investigation Team. On the 14th November 2019, the JIT released several intercepted telephone calls, revealing details about secure means of communication used between DPR fighters and Russian officials. The telephone numbers that were used are from the same series and appear to be provided by the Russian security service FSB.
As for the disinformation narratives about the Euromaidan: the spontaneous onset of the Euromaidan was an organic reaction by numerous parts of the Ukrainian population to former President Yanukovych’s sudden departure from the promised Association Agreement with the European Union in November 2013. The protesters' demands included constitutional reform, a stronger role for parliament, formation of a government of national unity, an end to corruption, early presidential elections and an end to violence - as can be read here.
Similar cases alleging US interference in Ukraine in 2014 can be read here and here.