Among the democratically-elected leaders that have been ousted were Jacobo Arbenz in Guatemala (1954), Salvador Allende in Chile (1973), Jean Bertrand Aristide in Haiti (2004) and Manuel Zelaya in Honduras (2009). Washington targeted all these leaders with economic sanctions and destabilization campaigns that created the economic chaos and humanitarian crises required to justify a military solution.
The common denominator in all those cases had nothing to do with democracy or human rights, it was the fact that those elected governments had the audacity to challenge US interests in the region. The fact that a Latin American government might prioritize the interests of its own people over US needs is unacceptable in Washington.
That's why Maduro has been targeted.