  Recent scanning tunneling microscopy experiments [K.P. Nuckolls et al.,
arXiv:2303.00024] have revealed the ubiquity of Kekul\'e charge-density wave
order in magic-angle twisted bilayer graphene. Most samples are moderately
strained and show `incommensurate Kekul\'e spiral' (IKS) order involving a
graphene-scale charge density distortion uniaxially modulated on the scale of
the moir\'e superlattice, in accord with theoretical predictions. However,
ultra-low strain samples instead show graphene-scale Kekul\'e charge order that
is uniform on the moir\'e scale. This order, especially prominent near filling
factor $\nu=-2$, is unanticipated by theory which predicts a time-reversal
breaking Kekul\'e current order at low strain. We show that including the
coupling of moir\'e electrons to graphene-scale optical zone-corner (ZC)
phonons stabilizes a uniform Kekul\'e charge ordered state at $|\nu|=2$ with a
quantized topological (spin or anomalous Hall) response. Our work clarifies how
this phonon-driven selection of electronic order emerges in the strong-coupling
regime of moir\'e graphene.
