Using the N-body+Smoothed particle hydrodynamics code, ChaNGa, we identify two merger-driven processestextemdash disk disruption and supermassive black hole (SMBH) feedbacktextemdash which work together to quench L$^*$ galaxies for over 7 Gyr. Specifically, we examine the cessation of star formation in a simulated Milky Way (MW) analog, driven by an interaction with two minor satellites. Both interactions occur within $sim$100 Myr of each other, and the satellites both have masses 5 to 20 times smaller than that of their MW-like host galaxy. Using the genetic modification process of cite{Roth2016}, we generate a set of four zoom-in, MW-mass galaxies all of which exhibit unique star formation histories due to small changes to their assembly histories. In two of these four cases, the galaxy is quenched by $z = 1$. Because these are controlled modifications, we are able to isolate the effects of two closely-spaced minor merger events, the relative timing of which determines whether the MW-mass main galaxy quenches. This one-two punch works to: 1. fuel the primary halos supermassive black hole (SMBH) at its peak accretion rate; and 2. disrupt the cold, gaseous disk of the host galaxy. The end result is that feedback from the SMBH thoroughly and abruptly ends the galaxys star formation by $zapprox1$. We search for and find a similar quenching event in {sc Romulus25}, a hydrodynamical $(25,mathrm{Mpc})^3$ volume simulation, demonstrating that the mechanism is common enough to occur even in a small sample of MW-mass quenched galaxies at $z=0$.
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