Actually, this is something that someone removed from the page, and now it's not clear: Odoacer put Pavia under siege because Oreste and the last Western Roman Emperor, Romulus Augustus, recovered there. Odoacer wins and sent the vessels of the Empire to the Eastern Emperor, thus ending the history of the Western Empire.
Odoacer destroyed (yes, I found this word on a book, even if someone removed it from the page!) Pavia to punish the city for the help given to the rival.
Then Teodoricus rebuilt the Palatium and the thermae. It was already an important city under the Goths, that is one of the reasons why the Longobard choose it as the Capital.