Yes but I have yet to understand...
That's right, you don't currently understand. It has taken several attempts to get you to even begin thinking critically about your sources and even begin to contemplate performing due diligence on them. You responded to information about your sources with a knee-jerk reaction to defend them. A conscientious person doesn't lash out others when it becomes apparent he understands less of a subject than they.
why they euthanize the animals? Are they just killíng or have some justification to it?
They believe that any keeping or control of animals by humans is "enslavement" and that such a condition is worse than death. (Except, of course, when it's used to produce the insulin that keeps one of their high-ranking officers alive. Then it's okay.)
The animals I keep personally are in a symbiotic relationship. My cats perform a service I value, in return for which I exercise care in enriching and prolonging their lives. My dogs perform a service I value, and would not be viable organisms (e.g., one is blind, the other was lame) without my ongoing care. It would be difficult, in my estimation, to call that cruelty.
The animals I eat as food were bred and raised for that purpose. Without the purpose, the species would not exist. Without the purpose, the individual animals would not exist -- at least in so many numbers. As I said, my brother-in-law's family operates a cattle ranch large enough to be seen from space. I have seen how the animals are cared for and treated in large numbers, on a large scale. When these animals die or otherwise render their service, it is to fulfill a purpose: food, clothing, protection, lifesaving medicines and other procedures. You hear about these things and knee-jerkedly equate them with greed and gluttony.
PETA believes in neither of these purposes. They have "rescued" thousands of animals, by which they mean they have removed thousands of animals from environments they deemed unhealthy or immoral for no reason other than that disapproval. But what to do with them then? They can't keep the animals themselves, because that would just be "enslavement" under different circumstances. They can't give them over to other caretakers -- again, just more "enslavement." They don't have the resources to rehabilitate all the animals for return to life in their natural habitats, even if such a thing would be possible. PETA tells you they are therefore pinioned by circumstances to euthanize the animals. Death is better than captivity in any form, in their mind.
But PETA is pinioned by nothing more than their own perverted moral view. They have explicitly adopted a no-compromise stance for their moral edicts (except, as noted, when it hits too close to home). This irrational approach cuts off reasonable alternatives, but PETA advertises itself as a "radical" organization and so obviously isn't overly concerned with being reasonable. To put it bluntly, perfectly good animals die by PETA's hand only to demonstrate PETA's political resolve.
Now stand there and tell me with a straight face that this is a better justification than the ones I gave you above for the reasonable breeding and keeping of animals. I dare you.
Even worse, the simplistic, delusional moral model put out by Ingrid Newkirk and others is based on the presumption that animals and humans are equivalent in all respects. Animal keeping is enslavement. Eating meat is cannibalism. This is not just hyperbole; this is what they actually teach. You seem to have fallen for it hook-line-and-sinker. Not only does this lead them unwarrantedly to exalt even the lowliest animal species, it leads them to devalue human life. This group feels fully justified not only in killing animals rather than letting them fall into "captivity," but in putting humans in danger. PETA encourages and gives money to militants who commit crimes against humans when they believe animals are at stake.
If they are odd, how they get so much donations?
Because of the flood of slick propaganda they send out, which omits the gory details of what they actually do and focuses instead on what looks good on paper. Just like you, many people don't exercise due diligence. If you get a glossy brochure telling you about rescuing animals from unsanitary and inhumane factory farms or circuses where they are tortured for entertainment, you would be inclined on that basis to fork over fifty bucks -- hey, it's tax deductible, and it seems like a good cause.
Obviously those brochures don't tell the darker side, which is that they can't (and don't want to) keep the animals they rescue so they just kill them. They don't tell you about fronting and funding the Animal Liberation Front and other violent criminal organizations. They don't tell you that they spend more money encouraging and defending these militants than they do actually rescuing and caring for animals. You have to look for these facts, and many people -- like you -- just don't bother to do that. PETA hires hotshot publicists to keep enough glossy information easily available and to dance around the more egregious exploits. They hire enough sharp lawyers to go after people who denigrate them.
But even still there are enough people who know all this about PETA and still contribute anyway. Just because something doesn't make sense doesn't mean you can't get people excited about it enough to support it.
I just have to check if from their POV.
We've given you the facts about PETA. There is no "point of view" that matters a whole lot after that. It's odd that you would want to go read their spin rather than to ascertain what the facts are.