Why do you put 名詞 plus の before ようだ, but you put 名詞 plus な before わけだ?

Question

I looked up the dictionary, and found "よう" and "わけ" are both grammatical nouns (形式体言). But why is the 接続 different?

Moreover, I found many sentence patterns have their own rules. Are there any universal rules which determine which form you should conjugate into?

Answer 1

It's because の emphasizes possession

AがBなわけだ → AがBであるわけだ

AがBのようだ → AがBの様子をしている

But の can also function as the copula, and ～であるよう can work, so both are viable. The meaning is just not as strong or obvious so the usage tends toward this.