There are downloads of paid 3d models but without showing it is payed

They can only steal the models that has 3D viewer, that is everything from sketchfab, some models from artstation and fab and few models from cgtrader. If you don't post your models on sketchfab and don't include 3D viewer files to your models elsewhere, you don't have anything to worry about. And it's nothing new, that situation is very well known for years, basically as long as there have been online 3D viewers, there always was and probably always will be a way to illegally obtain their content.

Yeah I remember looking to see if my models on sketchfab were elsewhere, and it came up with a site called Deep3dsea. Most of my models from Sketchfab on there under my name but I am not a member of that site.... I contacted Sketchfab about it and they said they knew about the site but nothing was done even after I contacted that other site as well. It's just something we have to live with I guess, and now with AI it's even worse :(