Because manufacturing lightbulbs today is a well established process and basically any manufacturer can produce them if they so chose, as opposed to 1925's situation. It also quite empirically is no longer a thing as LED bulbs can last up to 100k hours [1] and are often rated for 50k [2], as opposed to the cartel's 1k [3].

1: https://www.inlineelectric.com/lifespan

2: https://www.bulbs.com/learning/ledfaq.aspx

2: https://en.wikipedia.org/wiki/Phoebus_cartel

You don't seem to understand how modern markets work. See for example Coca-cola. Anyone can create a drink that looks like Coca-cola. However, we know it has a near monopoly on that segment of the market. Just because a product can be manufactured, doesn't mean that companies have the capacity to create and produce it at the scale needed to become profitable.

That's a separate subject to anti-competitive oligopolies. Let me doubt people are loyal to lightbulb manufacturers and that the situation is remotely comparable to one of the most powerful and well established consumer brands in history.

But since you brought up this subject, why should I care consumer brands are exercising their pricing power for as long as I have access to the low-margin alternatives? People paying $5 for takeout coffee at Starbucks doesn't affect me in any way. It would affect me if Coke and Starbucks prohibited the existence of competitors or extinguished them, but that isn't the case (for these examples at least, such anti-competitive behaviors do exist) as you have yourself implicitly noted in your comment.

> It would affect me if Coke and Starbucks prohibited the existence of competitors

In a sense they do, every Starbucks in existence is a store where a traditional coffee shop cannot be stablished. How many more Starbucks it takes to completely shut other competitors out of the market?

I don't think it's useful to debate fictitious scenarios. You know of a place where there are only Starbucks selling coffees? I can't think of one, as someone that never steps in a Starbucks, yet often buys takeout coffee in other fastfoods.

On the contrary, Starbucks is frequently -- maybe even usually -- the only place in a given area that serves fresh coffee of fair to moderate quality. You can get coffee in McDonalds or Burger King, but it's not very good, and the employees know even less about coffee than someone working for Starbucks. The absence of competition in that midrange market means that Starbucks faces relatively little pressure to maintain lower prices and higher quality.

I can only think of a single other dedicated coffee shop near my suburb of Cincinnati, and it's a cat cafe that serves dogshit coffee (or catshit, I suppose, and I'm not referring to the civet). At least they have cute adoptable cats to play with!