  GW190814 was reported during LIGO's and Virgo's third observing run with the
most asymmetric component masses (a $\sim 23$ $M_{\odot}$ black hole and a
$\sim2.6$ $M_{\odot}$ compact object). Under the assumption that this event is
a binary black hole (BBH) merger formed through the isolated binary evolution
channel, we reanalyze the publicly released data of GW190814 with the modified
astrophysical priors on the effective spin $\chi_{\rm eff}$, and further
explore its formation history using detailed binary modeling. We show that
GW190814 is likely to have been formed through the classical common envelope
channel. Our findings show that the properties inferred using the modified
astrophysical priors are consistent with those inferred by the uniform priors.
With the newly-inferred properties of GW190814, we perform detailed binary
evolution of the immediate progenitor of the BBH (namely a close binary system
composed of a BH and a helium star) in a large parameter space, taking into
account mass-loss, internal differential rotation, supernova kicks, and tidal
interactions between the helium star and the BH companion. Our findings show
that GW190814-like events could be formed in limited initial conditions just
after the common envelope phase: a $\sim 23$ $M_{\odot}$ BH and a helium star
of $M_{\rm ZamsHe}$ $\sim$ 8.5 $M_{\odot}$ at solar metallicity ($\sim$ 7.5
$M_{\odot}$ at 10\% solar metallicity) with an initial orbital period at around
1.0 day. Additionally, the inferred low spin of the secondary indicates that
the required metallicity for reproducing GW190814-like events should not be too
low (e.g., Z $\gtrsim$ 0.1 $Z_{\odot}$).
