If only the real world was a straight line, and there were nothing such as authoritarian coopting of collective efforts, resembling right wing fascist authoritarian, wearing the corpse of an attempted social movement.
Why animal farm exists
Why the 'national socialists' came for the communists and socialists first.
You're representing a high dimensional ecosystem with oversimplified boundings being flattened into a linear scale, and the 'horseshoe' is moreso adapting the simple heuristic to better represent the more complicated reality.
Sometimes the meaning of words is opportunistically changed, or the people directing a group change, and we actually have to comprehend and adapt to that.
A better representation of the political system is like a body where a bunch of organs seem to think cancer might be the best shape to be. Cancer as in 'defining wider boundings of surrounding systems as exploitable environment' usually ignoring how the surrounding body is literally necessary for sustaining life for the cancer itself. This is also where we would talk about things like instrumental convergence in natural/human systems.
So the linear line doesn't really explain the constant rugged individualism usurping spaces in our complex high dimensional social reality. Ergo horseshoe heuristic.