How could Euro bonds serve as a "safe haven" asset in the long run?

The German Bund has been the major safe-haven asset in the Eurozone despite the advent of the Euro. However, I noticed that there is mounting anticipation around a potential 750 billion worth of Euro issuance in coordination with the recovery fund.

The market consensus is that this is a positive for Euro bonds, but I still find the situation a bit perplexing. The commission has had years to promote the Euro (if they agreed that’s what they wanted to do), but it’s only now, faced with a pandemic, that significant issuance is undertaken. If it takes something as colossal as a pandemic for a meaningful increase in the volume of the Euro bond market, that’s not so reassuring for the future of the asset class.

Question

What evidence is available to suggest that the Euro bond is on a more widespread adoption trajectory in terms of being a safe-haven asset class (and not just a fluke of massive fiscal stimulus from the occasional black swan)?