But if you look at for example the Veiled Chameleon, who lives a very delicate existence in small pockets of forest in Saudi Arabia and Yemen; and see how the captive population in the US and Europe has ensured it's survival in the wild.
The veiled chameleon is not "delicate" in any way. Rather, it is one of the few chameleons that has proven itself capable of living in highly modified habitats, almost to the extent where it can called a synanthrope. In most of its range it is found at high densities. Gardens, plantations, etc, are just as suitable as its "original" habitat. There are however plenty of other chameleon species that
are extremely vulnerable: mostly species restricted to East/Central African highlands+species from Madagascar. The problem is that these threatened chameleons usually have proven rather delicate in captivity; little or no breeding despite attempts by specialists.
Platypus are susceptible to changes that could mean they become endangered in a relatively small time frame if something similar to what is happening in Tasmania ever made it's way to the mainland.
Overall the platypus can hardly be defined as particularly susceptible. At least unless you want to classify something like 50% of the worlds species as susceptible! Sure there are subpopulations that have declined (some drastically so), but quite large populations remain and there are no indications that anything like a species-wide crash could happen. Its distribution also spans over a fairly wide latitude, which itself works as a security against e.g. climate change.
The San Diego Zoo has bred 6 babies in captivity; who were born to Bai Yun since 1996. I have never heard of a Chinese zoo being as successful; but admit I have never researched if that is that case or not. By mere fact San Diego Zoo is mentioned as running one of the most successful Panda Breeding programs I just assumed China was not seeing the same levels of success- or else we would hear more about it.
Together, the centers at Chengdu and Wolong have bred more than 200, far outdoing everywhere else. The giant pandas outside China are essentially "ambassadors" of the species. Fine if they breed too, but not all that important to its captive population by now – even if zoos outside China always hail it as a massive step in conservation whenever one of their pandas give birth. While I have my reservations about the Chinese "panda farms" (as some spitefully have called them), they're the only reason we have giant pandas in captivity today*. The captive population is now at a level where it actually
can function as a security buffer should the wild population disappear, which however is unlikely. Releasing captive animals to the wild has never been easy. Regardless of species only a fool without any knowledge of reintroductions would expect the first attempt to be an unconditional success (interestingly, the people that want orcas released often seem to forget this, but that's another discussion). The dailymail article keeps the standard I expect from them.
* With the exception of the Mexican (etc), but that's clearly not enough to base a population on.
