Haftar may be a bastard, but he is an anti-Islamist bastard. The noose is tightening around Tripoli and Erdogan can’t send mercenaries fast enough to postpone the fall.
Libya is also a deeply fractured country, with deep hostility between urban, relatively well-developed Tripoli and the less developed area to the east. That area has strong tribal traditions and disputes Tripoli's efforts to control the country's oil and gas resources. Since much of those resources are smuggled out to pay for Russian and Turkish help, the rebel faction in the eastern part of Libya has ready financing for its war against the recognized government in Tripoli.
Confusion over the US and allied interests at stake in Libya, if any, is natural because our national security strategy is often publicly incoherent due to the risk of revealing too much unpalatable truth. Doing nothing is not much of a strategy in itself but here it seems the best approach. In essence, we are giving backing to the legitimate government in Tripoli and letting antagonistic interests and energies sort things out so long as US interests are not infringed and US rules and limitations are adhered to.