It wasn't announced as 'DOGE' but it was not a surprise; from August: "Former President Donald Trump signaled his willingness to offer Elon Musk a role in his administration in a proposed “government efficiency commission” if he wins the presidential election in November"[1].

In the Republican Party Platform 2024: "2. Rein in Wasteful Federal Spending. Republicans will immediately stabilize the Economy by slashing wasteful Government spending"[2]

[1] https://www.forbes.com/sites/siladityaray/2024/08/13/trump-b...

[2] https://www.presidency.ucsb.edu/documents/2024-republican-pa...