Yes — industry. From Wikipedia:
> Eighty percent of mined diamonds (equal to about 135,000,000 carats (27,000 kg) annually) are unsuitable for use as gemstones and are used industrially.[131] In addition to mined diamonds, synthetic diamonds found industrial applications almost immediately after their invention in the 1950s; in 2014, 4,500,000,000 carats (900,000 kg) of synthetic diamonds were produced, 90% of which were produced in China. Approximately 90% of diamond grinding grit is currently of synthetic origin.[132]
> ...
> Industrial use of diamonds has historically been associated with their hardness, which makes diamond the ideal material for cutting and grinding tools. As the hardest known naturally occurring material, diamond can be used to polish, cut, or wear away any material, including other diamonds. Common industrial applications of this property include diamond-tipped drill bits and saws, and the use of diamond powder as an abrasive.
As your quote points out, synthetic industrial diamonds have been available for many decades. But it is only recently that synthetic diamond gems have achieved popularity and price advantage for jewelry.
(Patents were really strong back then. Howard Hughes, Sr. became the richest man in the world by buying the patent for the drill bit. He then manufactured bits and rented them out for a fraction of the profits from the oil well.)
[1] https://www.slb.com/products-and-services/innovating-in-oil-...
[2] https://www.texasmonthly.com/being-texan/texas-primer-the-hu...
Diamonds are used in all kinds of things besides jewelry. Industry needs that economy of scale.
But there are also applications for larger flawless crystals in things like diamond windows, semiconductor substrate and microtomes. Recently you can even buy a diamond 3D printer nozzle for extruding abrasive materials like carbon fibre. These require better processes than the ones that churn out abrasive diamonds.