Atheism

Not all Christians are fascists, and not all fascists are Christians; while there is a pretty significant overlap between these groups, we have to remember that fascist atheists exist, fascists who belong to other religions exist, and anti-fascist Christians also exist (even though Christianity itself is an incubator for fascism).

I know this because I was raised in an atheist fascist household.

So Christo-Fascism is not redundant, it is just a common flavour that often comes together. To claim it is redundant is to claim that Christianity and Fascism are interchangeable—they are not, and it can lead us to be blindsided when non-christian fascists appear.

Fascism always appears in different flavours; otherwise recognising fascism would have been so easy that fascism wouldn't have been able to gain traction. Think of it like a pathogen, when we (the population) start developing an immunity to a certain variant, another variant gains which outperforms the older variant. Also, once enough time passes, older variants sometimes surface back, as the memory of the immune system fades away and we become more vulnerable to it.