this attacker did not get sloppy, they got control of a critical piece of free software, and got a still-not-fully-understood piece of malware in to, past whatever peer review we like to imagine we have, then got it uploaded into at least two critical linux distributions, past whatever peer review we like to imagine we have, and was only found, two years in to the operation, by pure luck and a very dedicated engineer.
I'm a tad reminded of https://xkcd.com/705/
We got so lucky here. We won't get lucky every time. We will have a massive breach one of these days.
But I would say it was also luck. If Andres hadn't been benchmarking on Debian Testing (or whatever system he found this on) this might have taken longer time to discover.