You have a puzzling, and, I think, bespoke, notion of "Machiavellianism". If a cancer patient undergoes painful therapies to cure the disease, is that Machiavellianism, because the ends, curing cancer, justifies the painful means?
I would say no. That's simply an example of doing something unpleasant in pursuit of a larger goal. Typically, when people use the term Machiavellianism they are referring to doing immoral and objectionable things in pursuit of personal goals. That's not really the case here at all.
Free people have no moral obligation to transact with one another. There is no moral obligation to permit people to your chess tournament and no moral violation in denying them. When we decide that the crimes of the Russian government, acting, at least nominally, on behalf of the Russian people reach a critical point we can decide to discontinue business and relationships with the Russian people.
Perhaps you think, as others in this thread have suggested, that this is something like a civil rights action. Indeed, in the US we have laws prohibiting businesses from denying service to people purely on skin color. In my view this is more of an ethical choice than a moral one, but even if you think it's a moral necessity not to deny service to someone based on their immutable characteristics, that is irrelevant. Russians are being denied service not because the world has suddenly become slavophobic, but as a condemnation of their country's crimes. Put another way, it would be wrong for a restaurant to turn away a customer because they are black, but completely understandable for a restaurant to turn away a customer because that customer is OJ Simpson.
I assume you would say that individuals are unlike countries, and I think that's true. Some individual Russians oppose their government's attack on Ukraine. Alas, there is no way to scope sanctions such that they hurt only people with the wrong opinions. There is a simple way to scope sanctions such that they hurt Russians though - i.e. make the sanctions apply to Russia. (And here I use a colloquial sense of the word "sanction" that I mean to extend even to non-governmental groups making decisions to refuse service to or interaction with Russians).
Finally, I agree with what I think you mean - which is that it's very possible for things to work out in ways other than what are expected. I expect that the majority of "things" work out roughly as expected throughout history but it is unremarkable when they do. If most of our choices were going awry civilization would probably unstable.
That said, I agree with the spirit - it's hard to predict the consequences of our actions. But, so what? It's hard to predict the consequences of sanctions and hard to predict the consequences of no sanctions. My own reasoning is: a war is too much, nothing is too little, and sanctions seem about right. Sanctions must hurt or they are meaningless. I would not want to see a headline like "Russian school hit by stray bomb, hundreds dead." A headline like "Russian chess player kicked out of tournament" seems about right for unintended consequences.