Python 2.7 was EOL'd at the start of 2020, and serious effort to move from 2 to 3 didn't start until around 2018, by which time Go was a very major player.

I meant when 3.0 was released. By the time 2.7 was EOL'd 3.0 had gained enough momentum to be a viable alternative. It was easier to just migrate to 3.0.

In 2018, I don't know if Go was a major player, both it and rust were still new-ish languages. There was still a concern of being able to hire devs if you used them, where as not so much in the past 4-5 years.

Major-ish. It was getting experimental module support around 2018; arguably go get was already better than Python's mess, but it wasn't great. It wasn't that widespread in industry yet - we could very rarely hire anyone with a Go background at that point.