When I see/hear ‘The Holocaust’ (upper case first letters), I have no doubt whatsoever that what is being referred to is specifically the murder of, predominantly, Jews by the Nazis in the 1930s and 1940s.

However, when I see/hear reference to ‘a holocaust’ (lower case first letters), that to me is a general reference to destruction or slaughter on a mass scale - e.g. ‘a nuclear holocaust’, or ‘the Grenfell Tower holocaust’.

The capitalisation or not makes all the difference. And I’m certain that the vast majority of people recognise the difference and have no difficulty understanding what is meant in each case.

All just my opinion only.