Upvote:0
The answer is very simple
Saarland was economicly a part of France and independent in name only.
The Saargebiet (after WW1) was a mandate that was restricted to 15 years during which everything produced was ceded to France, afterwhich a determination would be made to which country it would belong to.
After WW2, there was no restriction and it was Frances intension to make this a permanent solution. 1954 an agreement was made to allow a referendum to take place which led to reintegration to Germany (1957 politicaly, 1959 economicly).
Upvote:3
The formation of the Saarland was in a way imposed on Germany, but it also fitted into ongoing trends in national German politics which predate the 20th-century.
Reorganizing the "Flickenteppich"
If you look at maps running from the 15th century to the 20th century, there was a clear trend to unify the smallest statelets into bigger ones and to detach non-contiguous territories (many had been gained through dynastic marriage) from their rulers. Some of that has been imposed from outside, e.g. by Napoleon or by the Allies after WWII, but getting rid of the petty principalities was a desire of German nationalists, too.
Defining Germany
Defining just what Germany was, and who is is and who is out, had been an ongoing process within living memory of the formation of the Saarland. In addition to this German process, France had been trying to gain territory and influence on their eastern border.
Now to the specific case
The territory which became the Saarland in 1920 belonged to Prussia and Bavaria at the time. A century before, parts had belonged to the Grand Duchy of Oldenburg and to the Duchy Saxe-Coburg and Gotha (you will have to scroll down in the Wikipedia entry, the Principality of Lichtenberg isn't on the main map).
I believe that the idea of an unified Saarland was entirely in line with German political trends of the 19th century.
The Saarland had been French from 1680 to 1697 and from 1797 to 1814.
I believe that the idea of an independent Saarland detached from Germany was a long-running French ambition that was not supported by the population of the area.