Actually Kapp had only very few "supporters" even in the circles
@Anchises named.
IOTL it WERE actually the unions, that stopped Kapp.
They called a General strike, that especially in Berlin almost completly paralyzed the Kapp-"Goverment", no one, not the civil Service officials, not the policemen, not the post men, not even the garbage collectors followed their commands and they simply did not have enough armed followers, aka FreeCorps members at their disposal to force such Services.
Therefore, after a few days the spook was over with only very, very few casualties.
(Something, that would have definitly been very different, if the "Reds" would have intervened with force themself.)
But for the question of the OP (however implausible a successfull Kapp-Putsch may be) :
No
IMHO there would not have been a Holocaust. True antisemitism was relativly widespread, but it was Kind of a "civilized" antisemitism with some discrimination on a personal Level also by officials, but nothing institutionalized.
There were attempts to find arguements for an institutionalized antisemitism during the war. Then war Minister Wild von Hohenborn tried to initiate some statistical surveys to that behalf. But ist results were so ... "significant", that ist results were very quickly made "Highly Confidential" and then were ... somehow ... lost.
Wit the conservativey in conjunction with the Military in Charge, there would be no institutionalized, radical and patghological anti-semitism, as under the Nazis, who (Hitler, Streicher, Esser, Himmler (?), ...) WERE pathological antisemitists.
These guys, if thgey would ITTL rise to some Kind of promonence would have rather quickly been charged and put into prison if only for "disturbing public peace" with their radical, fanatical antisemitism.