On February 6, 2018, SpaceX launched the Falcon Heavy for the first time. The rocket lifted off from the same launchpad used for the Apollo moon missions. Its payload was a cherry red Tesla Roadster carrying a mannequin named Starman, with a copy of Douglas Adams on the dashboard and the message do not panic on the display. The car is still in an elliptical orbit around the sun.
The theatre was deliberate and effective. But behind the spectacle was something worth taking seriously as an engineering achievement. The Falcon Heavy is essentially three Falcon 9 cores strapped together. Coordinating the engines, managing the aerodynamic forces of that configuration, and controlling the vehicle through the various flight phases required solving problems that had not been solved before in quite this way.
The most striking moment of the launch was the simultaneous landing of the two side booster rockets. They separated from the central core, flipped, reignited their engines, and landed upright on adjacent pads at Cape Canaveral at essentially the same moment. The crowd reaction captured in footage from that landing site was genuine surprise, even from people who had been following SpaceX closely and knew what was supposed to happen. Watching it work was different from knowing it should work.
The central core did not land successfully, coming down too fast and destroying two of the three engines needed for landing before impact. SpaceX was transparent about this. The stated goal for the test flight was to not destroy the launchpad, and that goal was achieved comfortably.
What the Falcon Heavy represented was a significant increase in the amount of mass that could be launched to orbit at a cost that made certain missions economically viable that were not before. The comparison that came up repeatedly was with the Delta IV Heavy, which had roughly similar lift capacity but at significantly higher cost per launch. The question of whether Falcon Heavy would find a commercial market was real, partly because Starship, SpaceX's next vehicle, was intended to make even the Falcon Heavy look small. But as a demonstration that reusable heavy-lift rockets could work, and that a private company could build them, it moved the conversation forward.