Short answers, pulled from the story.
Stanislaw Ulam recalled a conversation with John von Neumann in 1958 about ever accelerating progress of technology. This discussion centered on changes in human life giving the appearance of approaching some essential singularity where human affairs as we know them could not continue.
I. J. Good speculated that superhuman intelligence might bring about an intelligence explosion in 1965. He proposed that an upgradable intelligent agent could enter a positive feedback loop of successive self improvement cycles causing an explosive increase in intelligence.
Vernor Vinge later popularized the term singularity in 1983 through an article claiming humans create intelligences greater than their own. His 1993 essay The Coming Technological Singularity argued it would signal the end of the human era.
Ray Kurzweil added to wider circulation with his 2005 book The Singularity Is Near predicting singularity by 2045. He reaffirmed these predictions in 2024 in The Singularity is Nearer.
Linguist Steven Pinker wrote in 2008 there is not the slightest reason to believe in a coming singularity because sheer processing power is not pixie dust that magically solves all your problems. Philosopher Daniel Dennett said in 2017 the whole singularity stuff is preposterous distracting from more pressing problems.