The economy was tanking way before the OAS sanctionz and the Peace Fair, those where just the cherry on top.

1) He moved the US' offices in the dominican customs over to offices inside the Banco de Reservas (created at US' request), which was a common strategy performed by the US at the time to reduce anti-american sentiment in Latinamerica. The same was done in Haiti... The DR "regained control of its customs" at the exchange of the US collecting the debt inside the national bank instead, exactly as it was done in Haiti a year before. 2) He reduced the country's external debt by issuing internal debt sucking all the dollars out of the private sector, and then issuing dominican pesos at a fake exchange of 1 dollar for 1 peso in order to pay that internal debt and basically robbing all of the dollars out of the internal bondholders... And what's worse... He performed this theft in a hurry only because Haiti sought to cancel its own external debt before the DR was (by greatly reducing government spending and through national sacrifice) under the rule of Dumersais Estime... The difference was that in Haiti they didn't out right robbed people out of their money like Trujillo did. 3) Under no circumstances can a dictatorship be considered "political stability"... Dictatorships whether they last 6 months or 50 years are not "stability" as uncertainty of its duration is inherently present at all times. 4) Before him there was plenty of industrial production in the DR (hell most of the rich families had already been stablished before he even was born, and under US occupation the economy was already thriving) what he did was "nationalized" it all and put it around his pocket, pretty much cementing the entire dominican economy around "state owned" inefficient monopolies sustained by slave work (political prisoners).

There was nothing good about the Trujillo era for the DR... Absolutely nothing.