"Aliens" or Non Human Intelligence isn't about believing. It's not a religion. It's about science and data.
Photo, video, infrared footage, radar data, radiation that can be measured. Not to mention non human craft and bodies in the hands of parts of the US government (China, and Russia apparently have captured such craft too), and in the hands of defence contractors.
Look at what Jake Barber and his Skywatcher team are doing. A 100% score in luring non human tech. Next step is to disable the craft and capture them.
If such a small team and budget can do this, it's likely much larger companies with much more resources and help from the military have started doing this decades ago.