The US has taken necessary action to root out corruption and terror financing through sanctions against Moukalled. Hezbollah has taken over Lebanon and put the country under Iranian-backed occupation — it's necessary for the US to support the Lebanese people against these tyrants.
These sanctions are just the latest imperial act by the US designed to strangle any and all opposition. The only reason Moukalled was sanctioned was to pressure Hezbollah into capitulation, something it will never do. Hezbollah and the resistance as a whole are stronger than the Western agents attacking Lebanon's sovereignty.
Though much of the media's attention has been focused on Moukalled and Hezbollah, it seems that the US's primary aim may be signaling to the head of Lebanon's central bank, Riad Salameh, that it will not turn a blind eye to his dealings with Hezbollah. Salameh has always presented himself to the US as a victim of Hezbollah's control over the country's institutions, but in reality, it seems that he is fully complicit in Hezbollah's financial goals.