I understand where you are coming from but it could be that your friends personal experience with their mom echoed what the doctor told them, or they were already considering it, so the Doctor saying that was the 2nd opinion. What your friends are dealing with is one of the toughest things you will ever go through as an adult child of an elderly parent... And there are never any "right" answers, only choices between bad options (especially as you slowly take away independence from your parents). You may be right that they did this because one doctor complained but it is far more likely that the discussion with the doctor was the end of a long road that you didn't witness.

However it is important not to conflate the idea of managing care for a parent as a family decision (like your friends are doing) & the issues of Conservatorship. Conservatorship always involves a court decision. It also involves payment to the Conservator from the estate of the person being managed.

The Conservator can be the one who manages those fees and payments (including hourly billing for their time and "miscellaneous expenses"). They also have the power to allow or deny legal representation to the person who wishes to be removed from their care. All of this sets up a framework that is easy to abuse.

The Conservator may be a close relative but in many, many cases they are court appointed people or relatives that are not close family. In these cases they have a specific financial interest in maintaining their Conservatorship.

Finally, Conservatorship is also used for mental & physical incapacitation (i.e., Britney) in addition to end-of-life care related to dementia/alheimers/etc... Cases involving these younger people are necessary but also are more likely to be when people need the ability to move back out of the status, or to be able to remove an abusive Conservator. This is where the victims are completely hamstrung under current systems (keep in mind that rules are different state-by-state).

So, while the situation involving your friend's mom is tragic and her right to manage her own life being removed is similar, it is actually not the same thing as what Britney is dealing with in her battle to end the Conservatorship.