  Removing cold interstellar medium (ISM) from a galaxy is central to quenching
star formation. However, the exact mechanism of this process remains unclear.
The objective of this work is to find the mechanism responsible for dust and
gas removal in simulated early-type galaxies (ETGs). A statistically
significant sample of massive (M_*>$10^{10}$M$_\odot$), simulated ETG in a
redshift range of 0.02--0.32 is studied in the context of its ISM properties.
In particular, we investigate the cold dust and gas removal timescales, the
cold gas inflows, and their relation with black hole (BH) mass. We also
investigate the evolution of galaxies in the dust vs. star formation rate (SFR)
plane and the influence of merger events. We find agreement with previous
observational works considering the timescales of dust and HI removal from
ETGs. When considering the dust-to-stellar mass ratio as a function of time in
simulations, we recovered a similar decline as in the observational sample as a
function of stellar age, validating its use for timing the ISM decline.
Moreover, we recover the observed relation between dust mass and SFR for
actively star-forming galaxies as well as for passive ETGs. We also show that
starburst galaxies form their own sequence on the dust vs. SFR plot in a form
$\log(M_{\rm dust, SB})= 0.913\times \log({\rm SFR}) + 6.533$ with $2\sigma$
scatter of 0.32. Finally, we find that type II supernova reverse shocks
dominate the dust destruction at the early stages of ETG evolution, while at
later times stellar feedback becomes more important. We show that merger events
lead to morphological transformations by increasing the bulge-to-total stellar
mass ratio followed by an increase in BH masses. The BH feedback resulting from
radio mode accretion prevents the hot halo gas from cooling, indirectly leading
to a decrease in the SFR.
