the heavy usage of slowking and blissey is part of why nidoking lost its attraction as a special wallbreaker, but nidoking is still a threat regardless of these tow factors. but with slowking, blissey and partly galarian slowking nidoking as it tougher as a special breaker, but its still a threat for unprepared teams with its wide coverage choices which are all sheer force- and life orb boosted. it is very easy for a substitute variant to tear up opposing teams. but the decline of nidoking happened due to other prominent threats such as dragapult, kyurem, heatran, tapu koko, tapu lele, and hydreigon need to be kept being at bay and slowking, blissey, and also galarian slowking do a good job at that meaning it automatically effected nidoking as well in the process.why has nidoking lost its prominece then comapred to before?
hopefully that helped :)