Beowulf
What angers the dragon?
Angers
Angers
Beowulf finds the dragon's treasure.
Beowulf stole a goblet from the dragon's lair.
"He had handled and removed a gem-studded goblet; it gained him nothing,
though with a thief's wiles he had outwitted the sleeping dragon; that drove him into rage, as the people of that country would soon discover."
Beowulf
It isn't Beowulf who steals from the dragon and brings on the initial anger. The text says "someone [unknown]managed to enter by [the dragon] and interfere with the heathen trove. He...removed a gem-studded goblet; it gained him nothing, though with a thief's wiled he had outwitted the sleeping dragon. That drove him into rage" (lines 2214-2219).
A thief outsmarted the dragon and stole a goblet, and that is what awakened his anger.
Beowulf goes on to fight this dragon as a result, and after slaying it (and taking a fatal blow in the process) he instructs his comrades to take the treasure.
Beowulf https://docs.google.com/document/d/1E_kdJ4Qd0lkCh5p7U0lCJ05-7oFf8R1HfasQX7T0ofI/edit