Tobias J. Moskowitz, a UChicago Economist, and L. Jon Wertheim studied home field advantage across all sports years ago, and concluded referee bias was real and was the driving force behind home advantage. It's explained in the book "Scorecasting"

For me, their findings were vindicated during the pandemic, when HFA all but disappeared. My guess is more recent decay might be because of VAR and goal line technology, which have become more integral to the game in recent seasons.