OpenCensus began in 2018.
Don't get me wrong, it's better for Google and Microsoft to collaborate on OpenCensus instead of continuing to develop separate client libraries for Stackdriver and Application Insights. It would be lovely if AWS joined too.
I just want to point out that there was a lot of community effort and vendor adoption around OpenTracing by 2018 that Google chose to ignore. If you want to reduce fragmentation and reimplementation, criticize that decision, not the existence of OpenTracing.