The current question, Was now really the right moment for Poland to demand concrete reparations from Germany? [duplicate], and in its earlier forms, focuses on the the Why of the earlier question, What are the pros and cons of demanding 1.3 trillion in reparation from Germany for the Polish government?.
While the later question may appear to be distinct, it has an answer already present in the earlier question. Specifically, the reason for demanding reparations, and to do so now, is the internal politics of the PiS party.
From one answer: For domestic purposes, they are seen as standing up for Polish interests. (See this Politico article and this CNN article on the domestic angle).
From another answer: It's about an internal political campaign to rebuild support for the ruling party. The combative stance towards Germany, is often used by this party, PiS, to mobilize its constituency. (Supported by this source.)
Should a question be marked as a duplicate if there's already an applicable answer on a different question?
Questions may be duplicates if they have the same (potential) answers. This includes not only word-for-word duplicates, but also the same idea expressed in different words.
If understanding why the questions are at all related requires a detailed explanation, the questions aren't duplicates, merely related.
From my perspective, I did not need a detailed explanation to understand that the questions were related and that the answer was already given in the earlier question; therefore, the later (your) question is a duplicate.
While I did not pay much attention to either question when asked in September 2022, when it appeared in the Review queue in January 2023, I examined both questions and reached the conclusion of the later question being a duplicate. I can't explain why others closed the question in September, but I suspect it was for similar reasons.