Why does the Mufti not provide evidence for his fatwas, such as determining the position of the opening takbir, following the example of some Muslim scholars?

The Mufti at IslamWeb does not issue any answer devoid of evidence. It is not a condition for the evidence to be a verse or a hadith; it may be a consensus (ijma'), an analogy (qiyas), or a fatwa from one of the scholars. The Qur’an and Sunnah are finite, while newly arising matters are infinite. A fatwa differs from research in that it is directed at the general public, and excessive detail in presenting evidence may hinder their understanding.