Well, without the cartel there could have presumably been bright white, 1000 hour bulbs on the shelf next to dim yellow 2500 hour bulbs, and people could have chosen accordingly.
Additionally, the companies set up a whole compliance regime with bulb testing and fines, not for bulbs being too dim, but for bulbs that lasted too long, which I think clarifies the intent more than anything else.
There were long-lasting bulbs on the shelf, but they were niche products because they produced poor quality light and were inefficient. Here's an example: https://www.youtube.com/watch?v=JQpqyt3oeqk . Note that it consumes 40 watts but produces the same light output as a standard 25 watt bulb.
