I think he's most often called a Russian asset because he has multiple apparent connections to the Russian government. Just looking up 'trump Russian ties' brings up multipledifferentarticles detailing ties which connect Trump to Putin. It's not necessarily proven, but the general view in media at least is: if trump is a foreign agent, he's a Russian one.
There's been memes on Chinese social media since at least 2020 calling him Comrade Chuān Jiànguó (川建国) and saying he's working to destroy the US to China's benefit. Chuan is just a sinicized form of Trump and Jianguo is a given name from the first decades of the PRC (Trump's generation) that means "to build/found the [Chinese] nation"
It's not a speculation. You misunderstood. He openly admits and acts and comments on how he loves his model for government and is going to be a dictator too. It's not a consideration. He is a lapdog. He is only accidentally also a Chinese asset.