In practice, it was liberals who enacted heavy sentences on crack usage.
California, an extremely liberal state, voted in a 72% majority referendum for the three strikes policy.
So, I’m just curious why liberals have some sort of lock in the minds of people as being on the “side of the poor”.
Incorrect. In 1994, when the three strikes legislation passed, CA was a purple state with a moderate Republican governor.
It is the anti-immigrant rhetoric around Prop 208 in 1996 that undermined the GOP in the state, by driving the majority of the young and non-white into the arms of the Democrats.
https://en.m.wikipedia.org/wiki/Political_party_strength_in_...
Also they do have a large portion of the working class - just not definitively over the white part who traditionally bear the name. Perhaps related to their strong hold on minorities that made them not stand out as a distinct bloc. Parts of their other coalition having views at odds with theirs and friction related is not new (see the Hard Hat Riots for one and environmentalists vs industrial workers). Similarly Republicans have long been reaching them on social issues as well - pre civil rights act related inversion even arguably.
Regardless of one's moral opinions facing their overtures largely rejected and power diminished why should the democrats try to serve them at the cost of others strategically? They aren't special or numerous enough which makes the political capital better spent elsewhere.
Blue-dogs exist and are run where locally favorable but they aren't nationally prominent for a reason.