We revisit and clarify the logic of the matrix string theory (MST) conjecture, relating the nonperturbative IIA string S-matrix in 10D Minkowskian spacetime to the strict large \(N\) Coulomb branch S-matrix of circle-compactified 2D  \(\mathcal{N} = (8,8) U(N) \) super-Yang-Mills (SYM) theory. The necessity of taking \(N\) strictly large is demonstrated by explicit Coulomb branch S-matrix element computations in the perturbative IIA regime. Using the MST conjecture, we make a number of predictions for the infrared behavior of the 2D SYM.