Either Go is a horrible language that did not learn anything or it is a language developed by some of the best engineers for a long time. If you are claiming that both things are true, then how do you explain it?
Google engineers are not some demigods or mythical geniuses and people should stop thinking that. They are successful within the framework of what they know, which is mostly C and C++. None of these people have academic background in language design, and it shows.
In other words, the same way you explain the success of eg Java.
Java was a safer C++. Go was a safer C. They both ignore a lot of good ideas from other languages, but I find it easier to forgive Java given its age and how much it’s caught up.
Java also had multi-billion dollar marketing campaigns.