On the face of it, I think they're all right, each side ultimately adding to the political instability. But on a deeper, more abstract level, I think the seeds of this crisis are the competitive social relations inherent in, and which dominate, 'exploitative' modes of production such as capitalism (and feudalism before that)—the former being the material basis for the continued social reproduction of the latter.
Unlike those who assume 'human nature' is a fixed, static thing that's naturally greedy, competitive, etc., I take the position that much of what we label human nature is fluid and changeable yet strongly conditioned by the world around us, including the economic 'base' of society, the way society reproduces itself. Hence the forces and social relations that are embodied within any given mode of production help shape and influence the ideas and social relations within that society (and in a global context, that includes those between nation-states). In A Contribution to the Critique of Political Economy, for example, Marx famously writes:
In the social production of their existence, men inevitably enter into definite relations, which are independent of their will, namely relations of production appropriate to a given stage in the development of their material forces of production. The totality of these relations of production constitutes the economic structure of society, the real foundation, on which arises a legal and political superstructure and to which correspond definite forms of social consciousness. The mode of production of material life conditions the general process of social, political and intellectual life. It is not the consciousness of men that determines their existence, but their social existence that determines their consciousness.
In a capitalist system, what Marx termed the 'coercive laws of competition' forces individual capitals to compete with one another and exploit labour as much as they can in the pursuit of profit; and at the same time, these coercive laws of competition force individual workers to compete with fellow workers, locally as well as globally, for jobs that provide the wages they depend on to survive. And this, in turn, influences and reinforces relations (individual, national, etc.) that are built upon or grow out of this socio-economic foundation.
Ukraine, then, can be seen as an extreme example and reflection of this competition, particularly between nation-states and especially the EU (and the US) and Russia. In the final analysis, most global conflicts have material, socio-economic causes underlying them, not ideological ones. Imperialism is really just the coercive laws of competition unfolding at the political level via the expansion and protection of markets and spheres of influence; and Ukraine is currently in the middle of an imperialist tug-of-war between national competitors that's tearing the country apart from the inside out.
Unfortunately, there are no simple solutions to these things, and god knows how it's going to turn out in the end. But regardless of the outcome, I can't help but wonder what a world characterized by a mode of production based on cooperation and free association (rather than competition and unequal social relations) might look like and how it might change things. Just imagine the possibilities.