Why did spain's regions have little autonomy before the 1970's?

Answer 1

There is an explicit assumption in the question that Spain's regions had little autonomy prior to the 1970s and while the general thrust of that is true, it is not wholly true. In the 1930s, under the Second Spanish Republic, Catalonia, Valencia, and the Basque Region were quite autonomous. It was during Franco's reign (1939-1975) that the regions lacked power.

Franco limited autonomy in the area for two reasons. First, he came from a strong nationalist perspective and did not wish to parcel out the country into distinctive areas. He desired a unified Spain. Second, Franco controlled Spain through the power of the Spanish Military and the Guardia Civil. Both of those institutions were national, so Franco reasonable favored the national government since it was the one supporting him.