Mussolini was fascist, but held left wing beliefs like welfare and relief for the poor and government intervention and ownership.

Welfare for the in-group is not (exclusively) left-wing. The Nazis had welfare for blonde blue-haired 'aryans' that produced lots of children. Also, neoliberal and conservative western governments love giving welfare to corporations and rich people. Even if your in-group is "all Romans" (in case of the ancient grain dole that Mussolini was inspired by) or "all Italians", if the motivation for welfare is to empower the in-group to exploit the out-group, it's right wing.

Government intervention and ownership are not (exclusively) left-wing. The original right wing - the monarchists in the French parliament - were pro-government intervention and ownership, with the government being embodied by the king. Government spending is consistently higher among Republicans than Democrats. Large ostentatious state projects with kickbacks for the in-group are bread and butter of pretty much every right wing government, from the massive Nazi government-owned holiday park Prora to the Space Launch System. Right-wing governments often forcefully nationalize projects run by the out-group, like Jewish shops in Nazi germany or Black Panther community support networks in the US.

The right wing may cloak themselves in the guise of the free market or of individual liberty or decentralization of power, or in the guise of community and centralization and rights that must be defended at the cost of freedoms. They will present themselves as underdogs and punks and outsiders or as rightful inheritors, powerful leaders, loyalists and patriots. Often they will switch narratives from topic to topic, going from underdogs fighting against the liberal elite who says you can't say slurs anymore to patriots bemoaning the lack of solidarity of people kneeling in protest at a flag.

The one thing that unites them, the one thing that is consistent, is to exploit and oppress the out-group to benefit the in-group.

Contrast communist authoritarianism and mass murder, which were generally justified as being for the good of all mankind.