It is true that TikTok's decision is autonomous, not directly dependent on Alphabet's performance. However, if TikTok invests in an event of this magnitude, it is because the market incentive and the visibility gain expected far outweigh the perceived costs, creating a balance where not doing so would be a dominated strategy. The asymmetry of information between platforms could also play a role, with TikTok possibly having more optimistic internal data on the return on investment of such events in the United States.