I mean, the Queen is an old lady and have only just stopped smoking after a lifetime, starting when she was 16 I belive. She knows she has to prepare the younger generations. Plus as a popular monarchy surviving on the good will of the people, they have to project a strong line of succecion and be visible to the people. Like monarchs of the olden days did on coins and medals.
On Saturday (as per tradition) Prince Christian will swear to the Council of State to follow the Constitution of the Kingdom and can thereafter the appointed to temporary head of state (Rigsforstander) if the Queen is unavailable.
I belive first time all three in the direct downwards line of succesion was on a job together, was in 2020, during the celebration of 100 years of Danish reunification with North Schleswig. All the royal commentators stressed the reason for all three to be a part of it, was in part to show a strong and stable monarchy and to show Christian the beauty of Sønderjylland (South Jutland), which the monarchy has strong links to, especilly after we got it back in 1920.
Kind of future proofing but also very natural. Seen in all monarchies, when the monarch is getting old: Was seen in the UK, and can be seen in Sweden and I think Norway too.
I have a soft spot for origami paper cranes.
Read or watch about "Sadako Sasaki and the Thousand Paper Cranes".
Spread a little peace and happiness wherever you go :)