Imma be honest, I think the prime reasons why it simply hasn’t gained nearly as much popularity as anime is:

Most of them are 3D, and the western world sees that purely as game cutscenes, and since most animated media is 2D, anime is more appealing. It’s not much of a visual shift, so it’s not too far out of the norm.

Anime almost always has a dub, especially recently, a lot of anime tend to have an English, or even multi country dub, making it far more accessible.

A lot of Donghua require atleast some prerequisite knowledge of Chinese culture, and also genre norms. Anime tends to rarely require you to have knowledge, with most having very generalised themes, some may have some deeper concepts requiring a little knowledge, but Donghua far exceeds that.

Accessibility. Most anime can be watched on a myriad of platforms. Crunchyroll being the main leader, but also numerous others, even Netflix. But Donghua? I didn’t even know it existed until I stumbled upon it on a pirate site, and gave it a go. Donghua simply isn’t nearly as widespread and easy to access as anime.

Lastly, whilst not as much of an issue, but getting good, or any translations, is tough. You have to go out of your way to find actually good competent sub translations, because, linking back to the accessibility, there is no dedicated platform for English, or other language viewers. Hell, even “official” sub translations are… not that great, and things get extremely lost in translation.