The 1 is converted to a complex number first, 1 + 0j, which then leads to an inf * 0 multiplication, resulting in a nan.
(inf + 0j) * 1
(inf + 0j) * (1 + 0j)
inf * 1 + inf * 0j + 0j * 1 + 0j * 0j
# ^ this is where it comes from
inf + nan j + 0j - 0
inf + nan j