Fiscal-Platform Interaction, R&D Investment, and Manufacturing Sustainable Development: An Analysis of Scenario Heterogeneity Based on Industrial Agglomeration

Amid the global wave of digital industrial transformation, the existing literature mostly treats fiscal subsidy policies and digital platforms as two isolated research subjects. Few studies construct an integrated governance framework for the coordination of fiscal subsidies and digital platforms, and related empirical evidence for manufacturing sustainable development under emerging-market institutional contexts remains insufficient. This paper adopts balanced-panel data covering 31 Chinese mainland provinces from 2011 to 2023. Following the triple-bottom-line principle of economy–environment–society, this paper constructs a multi-dimensional comprehensive indicator system measured using improved entropy-weight TOPSIS to evaluate regional manufacturing sustainable development performance, and builds a mean-centered interaction term index FIN×PLA to quantify the fiscal-platform interaction effect. Drawing on the suppression–mediation analytical framework proposed by MacKinnon et al., this paper takes R&D investment as the mediating variable and identifies heterogeneous transmission mechanisms. Different from observation-year dynamic grouping, this paper employs time-invariant grouping based on the 2011 baseline location quotient to classify samples, and further explores scenario heterogeneity driven by the matching characteristics between manufacturing agglomeration and producer-service agglomeration. The empirical results demonstrate that the fiscal-platform interaction exerts a significantly net positive effect on regional manufacturing sustainable development, and this finding survives multiple robustness checks and endogeneity corrections. R&D investment plays a partial-mediation role in the full sample. Mediation-effect types exhibit obvious scenario heterogeneity under different levels of producer-service agglomeration: regions with high producer-service agglomeration show full-mediation characteristics, whereas no valid mediation channel exists for low producer-service agglomeration subgroups. Further looking at the four agglomeration-matching subgroups, g1 (high manufacturing × high service) produces full mediation with countervailing direct and indirect effects; the mismatched g2 subgroup (high manufacturing × low producer-services) generates significant suppression–mediation, where the positive direct empowerment effect is offset by the negative indirect effect originating from crowded-out R&D investment; g3 shows no valid mediation channel; only g4 (low manufacturing × low producer-services) yields significant total policy effect accompanied by partial mediation. This paper establishes the theoretical logic of fiscal-platform integrated governance for sustainable manufacturing upgrading in emerging economies. It puts forward differentiated regional policy portfolios corresponding to four industrial-agglomeration combinations and proposes dynamic regulatory ideas targeting agglomeration-mismatch risks, providing quantitative decision-making references for advancing fiscal-digital synergy and green sustainable manufacturing.