UK Politics

Because not engaging in anyway serves nobodies benefit. This is explained in the article if you had read and understood it.

The whole point of the article is to realise that we are now in a different position than we were before Brexit. That applies to both the EU and the UK. You can either make the best of it or watch it get worse. The article is suggesting it's better for both parties that they make the best of it.

Some quotes that stood out to me:

Yet ultimately, the two sides will only be safe if their economies are growing as robustly as possible and generating the resources that will enable them to remain secure.

Starmer and Commission President Ursula von der Leyen should prepare an ambitious political declaration for their first summit in the coming weeks. It should prioritise foreign and security policy. But Brussels should not fear an upgrade to the core trade and economic relationship. As on security, this would be to mutual benefit. The zero-sum game of UK-EU relations since the 2016 referendum is finally over; the EU needs to recognise that closer co-operation is a win for both sides.

here are many reasons set out in the article describing possible positives for the EU and the UK. But why would the EU want to be closer with the UK when the UK has literally decided to go its own way, and then waddles back with its tail between its legs

So your entire position is that the EU is bitter over a bad relationship and is willing to hurt themselves to spite the UK? Are you sure you're not the Brexiteer?