>I wouldn’t go far as to say Von Neumann was smarter than Grothendieck
He famously recounted his inability to derive Heron's formula for the area of a triangle when he was a teenager (despite realizing that such a formula ought to exist via conceptual reasoning), and seems to have subsequently kept an unbalanced set of talents in the same vein.
Grothendieck was the best in class at abstract mathematical reasoning and some regard him as the best mathematician in the 20th century. The Heron Formula or “prime” example doesn’t negate that
He famously recounted his inability to derive Heron's formula for the area of a triangle when he was a teenager (despite realizing that such a formula ought to exist via conceptual reasoning), and seems to have subsequently kept an unbalanced set of talents in the same vein.