Want to know why everyone claims fascism is a product of the far right?
Read about the source: Giovanni Gentile
After you read what this philosopher believed and often spoke about, it will be come quite clear why fascism is projected to the opponents of the left. Because his views were more like the liberal left and marx that they could be easily interchanged.
For those who just want the executive summary:
https://www.dineshdsouza.com/news/fascisms-karl-marx/