You are mixing casual relationships. GPS was jammed because of the Ukrainian drone attack, it's a standard electronic warfare countermeasure and civilian planes are well equipped to fly without relying on GPS. And it's perfectly reasonable to close airports when you have a drone attack in the vicinity (e.g. it's done regularly in Moscow airports).

You can easily verify that the jamming has started _before_ the plane started to lose altitude. In the first place, your scenario makes little sense, since its useless to cover things with jamming while this cover will be immediately blown up by inspecting the black box records. And wouldn't it be better to land the plane on your territory for anyone attempting a cover up?