why is monopoly ( in economics) not alsways bad for the consumer?

the only time monopolys are ever good for the consumer is when the product is infrastructure intesive. you need electric wiring to and from every house to the power supply, so you want all the power lines going to one place, otherwise you have several different companies competing, and having to wire you up to their own power supply seperately. it just wouldn't work.

Controlled or guided monopoly can be a welcome thing for the consumer. It will not have any viable competition to erode into its sphere of operations or its territory. With good governance and a free-flow feedback system available the monopoly can progress profitably but equally equitable in terms of customer satisfaction.

If you have a bureaucratic type industry such as electrical generation and supply then a government controlled monopoly is not necessarily a bad thing but if the industry is in a dynamic phase such as telecommunications then it´s best to leave it to competitive forces to advance it.

because a firm does not have another firm to compete with it in a monopoly. therefore that specific market will have high prices, and not necessarily great quality because the firm can make its own rules with nobody else competing with them. if its a popular market especially, consumers have no choice but to buy with no other options.