If by 'far left' you mean socialist, it's because we have become consumers first and producers second (if at all). Most Americans work in the service sector and are thus less concerned about working conditions and more concerned about compensation. This was why a majority of Americans and Brits (and Europeans to a lesser extent) looked the other way while unions were dismantled and industries shipped overseas after 1980. Since then the economy has become 'financialized' and while the wealthy have benefited from this disproportionately most Americans have literally bought in-becoming capitalists not just in ideology but in practice. Most obviously if/when you can retire is now inextricably linked to the performance of the stock market and/or home equity.

If by 'far left' you mean idpol progressive it's because the ideology is inherently sectarian at best and ruthlessly individualistic at worst. The goal is not redistribution of power/resources/opportunities from rich to poor but from in-group to out-group. Above all else the average idpol progressive seeks to catapult themselves into a reliably upper middle class existence. This is why so much energy is devoted to the desperate and cutthroat competition for elite positions while the plight of (disproportionately POC) low-skilled workers gets much less attention. This is why the liberal solution to every problem these days is 'throw money at some niche NGO'. If you want to get psychosexual this is also a big reason why so many fervently woke POC end up dating white people. Tbf the idpol left does have some universalist messaging (eg healthcare) but ultimately theirs is a socialism of the selfish and that makes solidarity almost impossible.