I believe it was the same people, people that used to carefully plan how they'd use their 100kB of ram budget in C that then switched over to mission-of-the-week Python scripts.

The code that runs on Mars was always written by career programmers, not the rocket scientists. It was the mentality that they didn't have to carefully plan resource use, or even care too much about it, and if it didn't work, they could just ship a patch was just a giant cultural shock for them, because it was so different from how they wrote mission critical software in the last several decades.