First, it's exoplanet, then many many exoplanets. Then exoplanets with atmospheres, then with water, now with chemicals that indicate life.
Just like Mars. Viking 1976, weird results when testing for life. 1996, Mars Pathfinder, areography that looks like water formed it. Then rovers that find clays and other minerals that only form in liquid water. Then seasonal methane, and organic molecules in rocks.
They know. There's too much trickling out. There's ET life.