Somebody missed out on getting the perfect lawn ornament.
I fail how to see how it was a “strategically important cargo”. It is a cool hunk of iron and nickel. One of the largest known falls and the largest known strewnfield (in China). But effecting Russia not at all other than passing through there.
Something like that is very valuable so, by seizing it, Russia gets something very valuable under the guise of the law. Doing one thing and claiming another is standard operating procedure tor a totalitarian regime. For example, you do: Kill a dissident. You say: He fell out a window.