I suspect Madagascar is similar to Algeria and Morocco which, even if never controlled by the Axis, the Allies invaded anyway. French West Africa is somewhat more questionable on that front though.
Also, maybe it somehow represents Germany “trading” with its Vichy puppet (aka, looting them for occupation costs).
Its not. Algeria and Morocco were also Vichy, but those were not directly occupied by Axis forces. Germany did have a few police ( gestapo) elements for the purpose of rounding up some people. These areas and other Vichy areas did not “trade” with the Reich, however, indemnity payments for the war in 1940 were ordered and as a whole, the Vichy government was responsible to meet this obligation. So the truth is the entire group of areas under Vichy control had to make payments to Germany, but that was not really “trade” . Also, most of these areas outside of France proper, never made any contributions to satisfy that requirement, because frankly the terms were ridiculous.
It is also true that the Allies invaded Madagascar, The Levant States, Morocco, Algeria, and Tunisia…all of which were under Vichy control, but in most cases the resistance was of a very short duration and the opposition quickly came to be part of the Allies.
But to make them “German” is totally ridiculous.