The trigger for the intervention was the violent overthrow of power and the geopolitical turn of Ukraine; Russia had no soft power tools left to keep Ukraine in a neutral status.If I understand you correctly, you’re saying that Kyiv’s response to Ukraine’s internal divisions made peaceful dialogue impossible and left Russia no choice but to intervene.
Even if I were to accept your account of divisions and repression within Ukraine, you haven’t established why Russian military intervention was inevitable. Russia having an interest in the outcome doesn’t mean it had no alternative to invade.
There is also the chronology: Russia had already militarily intervened in Ukraine before both the April poll and the Odesa fire in May. Odesa cannot explain why that intervention began.
The USA and Europe for decades ignored Russia's concerns and security problems, remember the Munich speech of President Putin in 2007.
The Odesa tragedy is not a cause, but a clear example of the fact that no one was going to conduct a dialogue with the South-East, and that they would kill for dissent.