Spanish Republicans were openly backed by the Commies.
The Spanish Republicans STARTED the Spanish Civil War when they MURDERED the leader of the Falangist political party Jose Calvo Sotelo (what kind of "democracy" murders its political opponents?)
The Socialists/Commies had been murdering priests, nuns, landowners and anybody opposed to their politics off and on from 1931 to the outbreak of the civil war in 1936.
The Spanish Nationalists rose in reaction to the numerous atrocities and increasingly oppressive authoritarian rule of the Socialists/Commies.
The Spanish Nationalists/Falangists were not fascists. You could reasonably call them reactionaries, but they never had the goal of imposing totalitarian rule over Spain and indeed they did not. Religious minorities for example were tolerated. Many Many thousands of Jews fled to and through Spain prior to and during WWII. Franco's government did nothing to stop them.
Spain's economy grew tremendously under Franco and the Falangists peacefully stepped aside and allowed a Democratic government to take power of a now vastly wealthier Spain. The Commies would have delivered neither prosperity nor a peaceful transition to Democracy or at the very least, would have delivered the latter much later.
If I were Spanish and had to pick sides, choosing Franco over the Commies would have been an extremely easy choice. Viva el Caudillo!
Most likely had the Republicans remained in power, the Nazis may have invaded Spain, and seized Gibraltar.
Franco threw Hitler just enough bones to keep the Nazis out of Spain.
What kind of anybody executes a small-town mayor for having a “Three Kings” procession. Disgusting.