Oh but there's a bunch. For example:
-"The boundary of a boundary is zero" is a seemingly meaningless mathematical statement that just happens to be exactly equivalent to the differential form of Maxwell's equations of electromagnetism.
-Statistical mechanics is based on the assumption that some numbers are so large that they don't change when you add something to them, and other numbers are so large that they don't change when you multiply them by numbers that don't change when you add something to them.
-Sophus Lie invented the concepts of Lie groups and Lie algebras approximately 100 years before they would become useful, but then they become incredibly useful and critical for quantum mechanics. In a similar, but unrelated historical event, William Rowan Hamilton did the exact same thing with the Hamiltonian
-Galois Theory, which provides the basis for most of abstract algebra, was invented by a mathematician who died at the age of 20 in a duel over a woman who never loved him.
-The Riemann Hypothesis is probably the most famous unsolved mathematical problem, but what's lesser known is that some theorems have been proven by showing that they are true if and only if the Riemann Hypothesis is either true or false. Also, there is nothing that is true about the Riemann Zeta function that is not also incredibly interesting.
- The Continuum Hypothesis, which states that no sets exist which have have a cardinality between that of the rational numbers and the real numbers, has been shown to be independent of the seemingly otherwise consistent theorems that define set theory.
-Srinivasa Ramanujan existed.