Did you know that hydropneumatic suspension was tested on non-Citroën cars in the 80s?
Volvo was testing it in a modified 740 model where under the hood, hydraulic struts were fitted in place of the stock MacPherson struts.
Citroën’s Innovative Hydropneumatic Suspension — A Result of Adaptive Engineering
It was really the combination of adoption and innovation that was the formula for Citroën being distinct in automotive market.