That internal state where the world disappears, and it feels like every conceivable part of your consciousness is working towards a singular goal. Entering into this state was often accompanied by the feeling that time was flying, it was not unusual for hours to pass without notice in this state. Flow they called it, and because people in this state were incredibly productive, late stage capitalism became obsessed with achieving it.
At first the flow industry was just blog posts, fakesci books, and business school seminars. But as the pharma revolution kicked in, a series of breakthroughs led to Flowz, a family of drugs that could induce flow. When population growth stopped, and then began to retract, the economy could continue to grow, first with the uptake of Flowz use, and then with the series of drug improvements to induce higher states of flow.
And this is how the aliens found us. It turns out, that feeling of time flying was real. The local time induced by flow did indeed cause time to run slower. When the wave of distortion caused by a hyper optimized society of Flowz users finally propagated to the nearest interstellar civilization, the aliens detected the effect. It is easy to understand see why they invaded.