Not sure what your question means. One presumes that the EU's goal here is the obvious one, namely to make trade increasingly harder for Russia until they stop

Not sure what your question means. One presumes that the EU's goal here is the obvious one, namely to make trade increasingly harder for Russia until they stop invading other countries. To "impose a sanction" in this context is to apply a costly restriction to yourself, using the negative effect your self-restriction has on other parties to punish those parties, usually hoping that the negative effect is worse for them than it is for you. Any given trade happens because both parties want it; artificially making trade harder makes both parties worse off. The EU does not have to benefit from the intervention at all; they are apparently willing to pay that cost to make trade harder for Russia.