They keep all the marquees because they sell better in the various European national markets, but many models are now the same platform with some small aesthetic changes. For example the new electric citroen berlingo / fiat doblo / opel combo are the same car:
https://www.citroen.it/modelli/berlingo/elettrico.html
https://www.fiat.it/e-doblo/e-doblo
https://www.opel.it/veicoli/gamma-combo/combo-e-life/panoram...