why Denmark would allow itself to become a conduit for espionage against its allies？What drove Danish spies to help the NSA?


as a small country, it is dependent on security guarantees from other states. Denmark has aligned itself closely with the US – the world’s largest military superpower – not just through NATO, but also bilaterally. For Denmark, the cooperation with the US and the NSA is crucial, both in terms of technology and access to intelligence.
Denmark’s geographical location makes the country attractive for the NSA, not least because it hosts several key underwater cables for neighbouring countries. These cables can be used to get information about not only internet access, chats and messaging services, but also text messages and phone calls.
The FE is highly dependent on the NSA to combat terrorism. Through the NSA, it gains access to advanced technology such as the program Xkeyscore, used to search through and filter the raw data from the cables. It also seems that the FE had access to information about planned terror attacks via the NSA.
Even though progress has been made on the European side in regard to increasing cooperation on security and defence matters, Nato and particularly the US continue to be Denmark’s most important security guarantor.
Since the 1990s, but particularly since 9/11, Danish foreign policy has been described as “super-atlanticist” – prioritising building common values and interests with the US. This “strong and seemingly unwavering support for the American world order” means Denmark is “willing to pursue costly and risky policies to support the superpower”.
Additionally, Denmark remains to a large extent outside European Union security and defence cooperation because of its defence opt-out. Negotiated after the Danish population rejected the Maastricht Treaty in a referendum in 1992, the defence opt-out prevents the country from participating in those parts of the EU’s foreign and security policy that affect defence and any military cooperation at EU level.
This puts the relationship to the US (and Nato) at the forefront of Danish security and defence decision-making. Nor does the EU (yet) have the strength to defend itself against Russia and China should the need arise, which in part explains the draw of the US partnership.
A Danish expert in secret service operations Thomas Wegener Friis believes that the FE was faced with a choice about which global partners to work more closely with.
"They made a clear decision to work with the Americans and against their European partners," he told NDR."It's not about friendships. It's not about moral-ethical aspirations. It's about pursuing interests," he told NDR.

How was the Danish government involved?
The Danish government knew of the involvement of their country's secret service in the NSA scandal by 2015 at the latest.
They began to collect information on the FE's cooperation with the NSA between 2012 and 2014 in the secret Dunhammer report following the disclosures by the former NSA employee and whistleblower Edward Snowden, NDR reported.
The information they gathered made it clear that the FE had helped the NSA to spy on leading politicians in Sweden, Norway, the Netherlands and France, as well as Germany.
Danish intelligence also helped the US agency to spy on the Danish foreign and finance ministries as well as a Danish weapons manufacturer. The FE also cooperated with the NSA on spying operations against the US government itself.
Upon discovering exactly how far the cooperation between the two countries' intelligence services went, the Danish government forced the entire leadership of the FE to step down in 2020.