There was a cartel, but this is one of those "more complicated than it appears" situations. In incandescent bulbs, there is a real tradeoff between durability of the bulb, efficiency (lumens/watt), and brightness/quality of the light, for physics reasons you _can't_ improve one without degrading the other.

Since "quality of light" is a very difficult thing to market, there was an incentive to push "lifetime of the bulb" in marketing and just make the light quality increasingly worse. The cartel attempted to halt that by making everyone agree on a lifetime/quality to hit and not participate in a race to the bottom (and yes, there was also the obvious benefit to the cartel members of increased sales and profits, which they explicitly talked about in internal documents).

I want to be very clear that I'm anti cartels and I'm not trying to say "so this was all hunky dory", just that this was not (and these things very rarely are) a simple case of "they made the product objectively worse for the sole sake of more money". Instead, they chose a different point on the pareto-frontier of brightness/efficiency/lifespan that also had the benefit of making them more money.

But yes, LED bulbs are currently mostly garbage and have terrible heat/power management electronics which means that in practice you almost never get anywhere close to the theoretical life span increases (because the electronics die from overheating far before the actual LEDs themselves would go out), and finding out information on how well a given bulb brand does on heat/power management is essentially impossible.