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I think that you just read the sentence with a subtly different meaning than the one intended by the author.  Both spellings are correct.

Syntactically, you expect the subordinate clause to be governed by the entire previous clause (so as to supply a reason why authorities felt swindled), while in the actual text, the subordinate clause qualifies just a single word in the main clause ("estafadas"): swindled by what trick?

Semantically, it is reason versus means.