Collaboration does not push for a new system, it wishes for gradual improvements and it destroys parties that wish for real change. Look at the Italian Left for example which in the Historic Compromise made alliances with the Christian Democrats which ultimately weakened the Italian left and now even Italy's moderate social democratic party isn't doing too well, being 49 seats in the Chamber of Deputies behind Meloni's FdI. This gets worse the more radical you go, from social democracy (69) to socialism (4) to communism (0). Like how collaborating with their enemies weakened, moderated and neutralised the left in Italy, collaborating with the proletarian's enemies will weaken, moderate and neutralise the threat of the proletarian.