Ok, I'll bite. What exactly did Google do wrong here?

I'd be persuaded if you could show that a random walk through the recommendations ended up in far-right opinion some disproportionate percentage of the time. What you did was a goal directed search. At every point you selected the most right leaning perspective, and in the end you got where you wanted to go.

The only way to stop this from happening is to ban objectionable opinions from the platform entirely, or alternatively to disconnect them from the graph of recommendations. The latter is what YouTube's "limited state" already does.