Given the basic implausibility of the horseshoe theory, why do so many centrist commentators insist on perpetuating it? The likely answer is that it allows those in the centre to discredit the left while disavowing their own complicity with the far right. Historically, it has been “centrist” liberals – in Spain, Chile, Brazil, and in many other countries – who have helped the far right to power, usually because they would rather have had a fascist in power than a socialist.

Today’s fascists have also been facilitated by centrists

https://theconversation.com/horseshoe-theory-is-nonsense-the-far-right-and-far-left-have-little-in-common-77588

Same place happens to have a much newer article that concludes much the same.

https://theconversation.com/are-the-far-left-and-far-right-merging-together-thats-what-the-horseshoe-theory-of-politics-says-but-its-wrong-234079

Horseshoe models should be scrutinised for what they put in and what they choose to leave out. They emphasise values such as individualism, free markets and moderate policies, but register few of the social inequalities, exploitation and structural violence that often accompany them.

So while the left–right spectrum isn’t perfect, bending it into a horseshoe doesn’t do much to explain the strange political bedfellows of our times.