GNOME was backed by RedHat and other American developers, which included the likes of IBM, Intel, etc.
The bulk of QT and KDE developers are European; the only major European distribution, SuSE, went with KDE - but apart from that, the project could never attract the same level of investment as GTK-based efforts. It’s kind of a microcosm of the US/EU imbalance in digital tech.
Add to it that C++ (Qt) was never as popular as C (Gtk) in academic circles, which are major contributors of fresh developers to opensource in general.
I don't think the reason is really c++ vs c. But the regional aspect is spot on. Also when SuSE was bought by an American company (Novell), they fired all the KDE devs.
Another aspect is the licensing, GTK was licensed under LGPL way before Qt and RMS casting doubts on the legal aspect of KDE even after Qt was re-licensed under GPL didn't help.
All these played a role in the early 00s, nowadays the problems is mostly that GNOME has many more enterprise features and integration with other RedHat products and it is hard to catch on.
The bulk of QT and KDE developers are European; the only major European distribution, SuSE, went with KDE - but apart from that, the project could never attract the same level of investment as GTK-based efforts. It’s kind of a microcosm of the US/EU imbalance in digital tech.
Add to it that C++ (Qt) was never as popular as C (Gtk) in academic circles, which are major contributors of fresh developers to opensource in general.