Most of the Best Original Song nominees were performed (the one missing tune, “All the Stars” from Black Panther, was not performed only because Kendrick Lamar was unavailable), and all of last year’s acting winners were back to present awards this year.
This means none of these things were the reason people weren’t watching in the past.
The other reason the ratings rise is good news is that it will likely help stave off many of the changes the Academy was considering for this year that it ultimately went back on.