  We use a sample of $z=0$ galaxies visually classified as slow rotators (SRs)
in the EAGLE hydrodynamical simulations to explore the effect of galaxy mergers
on their formation, characterise their intrinsic galaxy properties, and study
the connection between quenching and kinematic transformation. SRs that have
had major or minor mergers (mass ratios $\ge 0.3$ and $0.1-0.3$, respectively)
tend to have a higher triaxiality parameter and ex-situ stellar fractions than
those that had exclusively very minor mergers or formed in the absence of
mergers ("no-merger" SRs). No-merger SRs are more compact, have lower black
hole-to-stellar mass ratios and quenched later than other SRs, leaving imprints
on their $z=0$ chemical composition. For the vast majority of SRs we find that
quenching, driven by active galactic nuclei feedback, precedes kinematic
transformation, except for satellite SRs, in which these processes happen in
tandem. However, in $\approx 50$\% of these satellites, satellite-satellite
mergers are responsible for their SR fate, while environment (i.e. tidal field
and interactions with the central) can account for the transformation in the
rest. By splitting SRs into kinematic sub-classes, we find that flat SRs prefer
major mergers; round SRs prefer minor or very minor mergers; prolate SRs prefer
gas-poor mergers. Flat and prolate SRs are more common among satellites hosted
by massive halos ($>10^{13.6}\,\rm M_{\odot}$) and centrals of high masses
($M_{\star} > 10^{10.5}\, \rm M_{\odot}$). Although EAGLE galaxies display
kinematic properties that broadly agree with observations, there are areas of
disagreement, such as inverted stellar age and velocity dispersion profiles. We
discuss these and how upcoming simulations can solve them.
