The title misled me here, I think. It sounded like an indictment that Temu stopped showing Google ads in its product then its ranking in Google Play dropped, but I don’t think it’s that.

Sounds like Temu was paying for ads to get users, and without those ads people stopped turning to it for shopping. Also,

The timing coincided with the Trump administration’s hardened stance on Chinese imports, raising tariffs to 125%

Perhaps the actual main factor.