I guess the choice of BTC but the scammer(s) was based on its much bigger popularity relative to Monero (many people have a few satoshis somewhere, but not many have some monero lying around)

How did you find that so quick?

These transactions were sent from a vanity address(es) [1], and in this case they're used to spam the recipient with implied messages, specifically about their poorly viewed scam--take it as a 'l33t' way of sending a message, hence the amount on the last tx. Another notable one was the EnjoySochi, as in the Olympics, transactions that spammed the network for a while 6 years ago [2].

1: https://en.bitcoin.it/wiki/Vanitygen

2: https://bitcoin.stackexchange.com/questions/22404/why-is-enj...

https://tokyo2018.scalingbitcoin.org/transcript/tokyo2018/ho...

https://arxiv.org/pdf/1704.04299/

Basically, the chaff transactions go to/from wallets actually owned by people. If you analyze enough of the chaff transactions, especially when the XMR that made them up is respent, you can deanonmyize users.

This is why people recommend you do not reuse wallets often but that still does not solve the problem.

Zcash I think is secure, or is per most analyses I've read.

https://tokyo2018.scalingbitcoin.org/transcript/tokyo2018/ho...

https://arxiv.org/pdf/1704.04299/

Basically, the chaff transactions go to/from wallets actually owned by people. If you analyze enough of the chaff transactions, especially when the XMR that made them up is respent, you can deanonmyize users.

This is why people recommend you do not reuse wallets often but that still does not solve the problem.

Zcash I think is secure, or is per most analyses I've read.