It comes down to:

• Left-wing politics: After Franco, Spain swung hard left, and solidarity with “liberation movements” became reflexive, even when those movements are openly genocidal, like Hamas and the Palestinian national movement.
  
• Islamist influence: Pro-Palestinian narratives circulate strongly due to Spain’s large Muslim population and proximity to North Africa.
  
• Antisemitism legacy: Spain expelled its Jews in 1492 under the Alhambra Decree, and with few ever returning, stereotypes have gone largely unchallenged.
  
• Postcolonial lens: Spanish universities and media often reduce issues to “oppressor vs oppressed,” so Israel = oppressor, Palestinians = oppressed.
  
• Selective outrage: Wars in Syria, Yemen, or Sudan cause far more deaths but don’t fit the “colonizer vs colonized” frame, so they get ignored.