Short answers, pulled from the story.
Ralph H. Baer devised the concept of playing simple spot-based games on a television screen in 1966. His idea became the basis of the Magnavox Odyssey, released in 1972 and widely recognized as the first home video game console.
Console manufacturers sell hardware at little to no profit, sometimes at a loss, and recover revenue through licensing fees on every game sold. The industry-wide rate has generally worked out to a thirty percent royalty paid to the console manufacturer for each game sold on their platform.
Consoles are sold on a cycle of approximately five to seven years, grouped into generations by similar technical capabilities. Manufacturers have designed consoles with five-year product lifetimes, though more recent generations have been planned for lifetimes of seven to potentially ten years.
Multiple factors contributed, including competition from lower-cost personal computers. A central cause was that numerous third-party developers flooded the market with poor-quality games for the Atari 2600 and Intellivision, making it difficult for even quality titles to sell.
The Nintendo Switch has sold over 155,920,000 units, making it the highest-selling console listed in the source data. The PlayStation 2 sold 155,000,000 units and the Nintendo DS sold 154,020,000 units.
The current market is led by Sony with the PlayStation brand, Microsoft with the Xbox brand, and Nintendo, which currently produces the Switch 2 and Switch consoles. The three form an oligopoly in the console market.