It wasn't about performance; GTK (or rather a GTK-based framework called Hildon) continued to be the default toolkit all the way to Maemo 5 ("Fremantle"), which is what shipped on the N900. It was also what Intel used on Moblin, the OS that was supposed to merge with Maemo to become MeeGo.
The issue with QT was all about Nokia: QT was supposed to save the Symbian platform, and also provide an on-ramp to Maemo (at least in theory - in practice nobody was really committed to that...). So the Maemo folks were obligated to switch to QT, which they did fairly easily; the result was what shipped on the N9, effectively Maemo 6 ("Harmattan") rebranded as "MeeGo 1.2".
In short: QT was adopted to please the Symbian people, and it was all for nothing anyway. That suited me just fine when first announced (Hildon was an under-documented mess of C with obsolete and unusable Python bindings, whereas QT had first-class wrappers like PyQt), but many Maemo old-timers never really warmed to it.
The issue with QT was all about Nokia: QT was supposed to save the Symbian platform, and also provide an on-ramp to Maemo (at least in theory - in practice nobody was really committed to that...). So the Maemo folks were obligated to switch to QT, which they did fairly easily; the result was what shipped on the N9, effectively Maemo 6 ("Harmattan") rebranded as "MeeGo 1.2".
In short: QT was adopted to please the Symbian people, and it was all for nothing anyway. That suited me just fine when first announced (Hildon was an under-documented mess of C with obsolete and unusable Python bindings, whereas QT had first-class wrappers like PyQt), but many Maemo old-timers never really warmed to it.