>>718829674
Because of the lore. Minthara is a female noble drow from Menzoberranzan and outside of extremely rare examples they all become clerics of Lolth. That's the norm since the days of the original Drizzt novels. Here's a random post I quickly found that addresses this in the paragraph. Check the date! Now I can't tell if Larian or 5e fucked up this in the meantime or if they simply treat Minthara as one of the exceptions but this shit was established decades ago.