In [15] (see also [20]) Schellekens proved that the weight-one space V-1 of a strongly rational, holomorphic vertex operator algebra V of central charge 24 must be one of 71 Lie algebras. During the following three decades, in a combined effort by many authors, it was proved that each of these Lie algebras is realised by such a vertex operator algebra and that, except for V-1 = {0}, this vertex operator algebra is uniquely determined by V-1. Uniform proofs of these statements were given in [42, 26].In this paper we give a fundamentally different, simpler proof of Schellekens' list of 71 Lie algebras. Using the dimension formula in [12] and Kac's "very strange formula" [28] we show that every strongly rational, holomorphic vertex operator algebra V of central charge 24 with V-1 not equal {0} can be obtained by an orbifold construction from the Leech lattice vertex operator algebra V-Lambda. This suffices to restrict the possible Lie algebras that can occur as weight-one space of V to the 71 of Schellekens.Moreover, the fact that each strongly rational, holomorphic vertex operator algebra V of central charge 24 comes from the Leech lattice Lambda can be used to classify these vertex operator algebras by studying properties of the Leech lattice. We demonstrate this for 43 of the 70 non-zero Lie algebras on Schellekens' list, omitting those cases that are too computationally expensive. (C) 2021 Elsevier Inc. All rights reserved.