system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why the Spanish civil war drew so much influence from outside powers? What was its signifigance at the time?
gpt
It was a cause celebre for left-leaning Westerners because there was a democratically elected leftist government overthrown by a military coup.  It was a matter of great public attention, kinda like how Kony or Darfur took off in the recent past.  So, individuals and governments with sympathetic political leanings had a situation that pitted a like-minded elected government against a coalition of the traditional institutional enemies of the left: royalists, the military and the church.

On the opposite side, the elected government was a European traditionalist's worst nightmare.  They were opposed to the church and king, socially progressive and were viewed by many as a threat to the fabric of European identity.

In essence, an internal Spanish struggle became an ideological proxy war in a very liminal period in history.  The old order had just led to WWI and the Great Depression, and people were trying to decide in what direction to chart their future.  Communists and Socialists flocked to the Republican cause, Fascists and Nazis to the Nationalists.

It became a test by which three new powers, Stalin's USSR, Hitler's Germany and Mussolini's Italy, could test both their newly developed military hardware but also their global influence.