Why did the preacher mention his desire to marry off women over thirty, even though he knows that Allah might have decreed for them not to marry until this age?

Delayed marriage is part of Allah's decree, but it cannot be definitively stated that a woman will never marry. A Muslim is obligated to strive and rely on Allah, and to contend with destiny by destiny, and to ward off evil with good, as Sheikh Abdul Qadir Al-Jilani and Ibn Taymiyyah said, citing the hadith (definition): "Be keen on what benefits you, seek help from Allah, and do not lose heart," and the hadith: "They are from Allah's decree."