What is the quid pro quo?

> Additionally, they [Germany] will visit and learn about French nuclear weapons facilities and infrastructure

This is a very bad development for France, the way this is going they will likely again give away their strategic capabilities...

The benefit for France is further weakening American hegemony. Right now the US dominates European alliances throughout Europe. America's recent turn away from Europe destabilizes the entire continent, including France.

The American nuclear umbrella forces a lot of countries to assent to American policies, even when it's not their preference. Creating a new world order will require somebody to provide the same level of protection that the US used to provide. It costs France very little to assert that they will protect their allies, using weapons they already possess.

How does this benefit France?

The way this is done and going this is also weakening France because it seems to be done in a way that gives more say and insight to foreign entities, especially Germany and the EU. So this is weakening the US' position in Europe to strengthen the EU's and Germany's, especially in defence, which in this case actually makes France's position worse.

It makes France's position stronger in the same way that the former alliances made the US stronger.

The US is throwing that away, and I'm inferring that you think that this is also a good thing. If that's the case, I'm not sure I can convey why it is that being a leader among allies gives you more power than you lose by having to take the opinions of your allies into account. But the US did consider that a good idea for a very long time, during which it became the leader of the free world.

You'd be right if we were talking about an alliance but the situation in Europe is not an alliance, it is federalisation under the EU, which is progressing by moving into defence. This is what is going on. The writing on the wall here is that this is a step towards further loss of sovereignty and loss of strategic know-how, not an "alliance", similar the project of building France's next fighter jet 'together' with Spain and Germany (who have zero experience), which is dissolving French technology, industry, and sovereignty into the EU/Germany.