Ask HN: How do people create those sleek looking demos for startups?

Ask HN: How do people create those sleek looking demos for startups?
132 comments on Hacker News.
I have been seeing people build product demos or show off their updates via videos - complete with zooming in on the active function and all. How do they make it? Can't find any straight forward tools online for this. Ex: https://ift.tt/L0ZkWoV