To understand anything Russian government does, you need to understand that they aren't a government in the way Western democracies / republics / monarchies understand the function of the government. For someone with largely humanistic outlook on life, the function of the government is to try to make sure that what's being governed prospers. Prosperity may be understood as "more riches for the rich" or "redistribution of wealth" or anywhere in between. But the basic idea is to make things better, at least for some sub-group of thus governed subjects.
Russia is operated by straight-up criminals. And I don't mean white-collar corrupt politicians. They are literally people who committed often very violent crimes. For instance, Putin is implicated in a number of "hits" on law enforcement officers, investigators etc. He was not the one executing the "hits", but he was likely directly involved in the crime. A lot of his associates have done often long time behind bars. For example, his puppet assigned to rule over Ukraine (the one who was deposed in the "revolution of dignity" which set in motion the present conflict) started his career as a gang robber: he, with his friends broke into an apartment, tortured the owners while taking their belongings.
These people have a mental model of the world defined by the prison lore. They have a bizarre set of rules which define what honor is: "honor" (the prison kind of) is the central value / virtue in this system. In this model, the world is divided into "suckers" and "men". "Men" are allowed to humiliate the "suckers" in whatever way they want. In fact, if they don't, they might as well join the "suckers". In this system, anyone who shows any kind of compassion to the "suckers" is him/herself a "sucker". Europeans or anyone who wants to live in a society that values any human life thus is automatically a "sucker".
This is why Russians think and treat Europeans with contempt and disdain. They don't think it to be immoral to steal from a European, or to assault one etc.
It's also "honorable" to accept the risks associated with humiliating the "suckers". To prove how much of a "man" someone is that is. It's actually better to die while proving your place is among "men" than to surrender and live like a "sucker". So, they don't care about international consequences of their sabotage in France today. At least not in the sense how another European country might've cared, should they engage in something similar.