People realized it all along. It just wasn't the time for everyone to say so at once.

Mourning time is that time.

It won't last forever. Mourning doesn't, and shouldn't, last forever. Which is all the more reason to make it count now, when it is appropriate.

I suspect that this has something to do with the competitive nature of human beings. Publicly praising/endorsing a famous living person on one hand gives him more power, and on the other hand encourages antagonism from the detractors/enemies/competitors of that person because praising/endorsing someone is an act of aligning with that person.

Giving power to others is not something human beings naturally want to do. Neither is inviting opposition. When the subject of the praise or endorsement is dead, the whole equation changes. Dead people have no power over you, and whatever enemies or competitors they used to have are usually no longer opposed to them.

Just my two cents. It would be interesting to have a way to test this theory.

I think it took his death only to make the realization (and discussion) simultaneous.

Heck, I had been thinking about his impact this past weekend, and I've spent a grand total of two dollars with Apple (and own no Apple hardware).