Cloud service investment in P2P2B mode is one of the key strategic decisions of Industrial Internet of Things (IIoT) platforms. An evolutionary game model consisting of IIoT platforms, leading enterprises, and potential customers is constructed to study the strategic choices of IIoT platforms in public cloud R&D investment and private cloud R&D investment and their ecological co-operation with leading enterprises. The results show that although the public cloud has data leakage potential, the higher returns to scale will still attract IIoT platforms to invest in public cloud R&D, while the high willingness to cooperate with leading enterprises during the platform construction period will prompt platforms to invest in private cloud, but as the proportion of collaborative R&D with leading enterprises increases, the platforms will change their investment strategies. The factors driving the cooperation of leading enterprises can be direct factors such as cost benefits and technology enhancement, as well as indirect factors such as scale benefits and data leakage probability. Finally, the system stabilisation strategies of IIoT platforms in the start-up, platform building and ecosystem phases are explored based on the platform life cycle and corresponding management insights are obtained.