Monopoly and open source dont mix. I can't think of an open source project that became monopoly by itself, without the continuous backing and pushing of its parent company. And there were/are plenty of monocultures in open source (apache / mysql / nodejs / Linux) that was rather a good thing than bad.
https://twitter.com/dhh/status/1174702952411303936
> "Yes. Monoculture in open source is scarcely better than monoculture in closed source. Monopolies of all stripes are bad for the web."