Real-life football doesn't work like that. United finished second in 2018 and to many fans, pundits and bookies they were a sure bet for the title in 2019, but instead they dropped down to sixth.
My memory is shit but I don't recall anyone thinking we were a sure bet.
I looked up the odds though. City had just got 100 points and were 8/13 to retain the title. United were 15/2 and third favourites behind Liverpool (4/1) despite finishing above them.