Casinos that are registered in Russia have to pay taxes on their earnings. Tax money goes into the Russian budget, and then this money supports the war, so it is somehow related to that war. The less money Russian casinos make, the less money there will be to prolong this war. The sooner it ends, the better, so boycotting Russian casinos is a good thing.
You have the same opinion with United State and several Europe country when talking about tax budget from casino gambling on Russia use for war invasion to Ukraine. I think is not true because all gambling casino platform never support with war invasion and they not have relationship with war. I think although have several casino gambling pay tax but not use for war invasion and as legal casino need to pay tax depend on country building.