TikTok is on Google Cloud. If it moved to Azure it would be one of its largest customers. This is why Microsoft wants a controlling interest but not to own it outright.
Its China version Douyin also uses a mix of Aliyun and their own infrastructure, so ByteDance likely have plenty of experience operating in multi/hybrid cloud environment.
I also suspect that Google Cloud's learning resource in Chinese is fewer than AWS/Azure.
Yes, that's true. But it's not like there are a lot of learning resources in Chinese for AWS/Azure, either. At least compared to Aliyun (Alibaba Cloud). So likely it doesn't matter.