ShadowCash was de-anonymized because the developers had adopted ring cryptography from CryptoNote and applied it to the Bitcoin Core codebase. In doing so, they had to modify certain parameters as the underlying elliptic curve used in the two protocols are different.

What happened was that they chose to hash some values that allowed someone, i.e. Shen Noether from Monero, who knows some basic Linear Algebra and Cryptography to apply a type of Gaussian Elimination to obtain which public key was used in the supposed anonymous send if someone wanted to use Ring Cryptography to hide the fact they are the sender. This, as you mention, de-anonymizes their chain, since it was incorrectly implemented.

A fix was found by a different team of developers (I forget by whom at the moment) and, from what I could tell, the dev(s?) seemed to have a firm grasp on the underlying mathematics and subsequently released his/her/their solution as a clone of ShadowCash.

A week or two later, the Shadow Team adopted precisely this fix.

Now, this is also fundamentally different from stealth addresses, which masks the receiving address, and not the sender address.

I can confidently say that both stealth addresses and the use of ring cryptography to anonymize both the receiver and sender in a transaction, respectively, are more powerful technologies than 'washing' and using TOR. To think that this is a 'gimmick' or a 'fad' to raise the market cap and to believe that these are 'false' claims (even by DASH, as the mixing that is done is, for all intents and purposes, a "practical" solution) about how much privacy is obtained is a gross misunderstanding of the mathematics.