There are more, better and larger Open Source projects now than ever before. Over the last three decades, the general knowledge about Open Source has increased a lot, and developers in general are now more likely to do Open Source and to have contributed to Open Source than they were in the past.
The way we produce Open Source has also changed drastically. We use different and better tools, we have better services provided gratis or at low cost, we have to a large degree switched to other languages and there are indications that the licenses used are changing over time.
We all have much better Internet connections that allow us to communicate better and more. We have more elaborate communication services. The use of computers is more widespread, and thus the potential of more contributors.