Goku was an Evil God talent who completely shook all demonic sects. Alm and Bruno had no ideas, but even the Three Extremes Sect had some crossed and subtle information about it.
Even with the recognition from the Tablet of the Malevolent God after the test, most didn't take it seriously. He was a genius above all geniuses, so what? How many geniuses die every day? Being above doesn't mean he's immortal.
But the grand Goku made a point to shake all their beliefs. In the first test, where everyone, and even the patriarch on his first attempt, almost died, he mercilessly massacred... then, the entire city witnessed an elder with a whole realm above him being brutally thrown into the air with just one of his blows, nothing made sense.
