By refusing to invite Russian President Vladimir Putin to the WWII commemoration ceremony Poland attempts to turn Belarus and Russia against each other. They hope that if [Belarusian president] Lukashenka comes to the ceremony and Putin does not, there will be bad blood between two of them.
Latvia has no sovereignty in the EU. It has its flag and coat of arms but virtually no economy is left. The country lost a third of its population and its foreign policy is totally dictated by Brussels and Washington with no space for an independent policy left.
Latvia is a sovereign country, which determines its domestic and foreign policies.
See earlier disinformation cases alleging that Latvia is a US vassal state, that the Baltic states pursue anti-Belarusian policies as instructed by external actors, that Lithuania is a "typical dying young democracy", and that the Baltic states are dying because they chose not to be with Russia.