How to understand the phrase?

[Alexey]

Hello!
In the "Treasure Island" by Stevenson there is a phrase "He whipped out of sight in a moment, leaving Silver to arrange the party, and I fancy it was as well he did so.". Could You help me understand "it was as well he did so" – what it means and why?
Thank You in advance!

[solzen]

It means that it's probably better that he left and Silver arranged the party alone.

If your friend wants to see a movie but doesn't, you might say "It's just as well, it was a bad movie." It's good that a situation happened the way it did (Silver arranged the party, your friend didn't see the movie).

[engnative]

"it was as well he did so"

This means. It was a good reason.

It also means: if it was you, you would of done the same thing.

"He whipped out of sight in a moment, leaving Silver to arrange the party, and I fancy it was as well he did so."

Here is the same sentence re-worded:
He whipped out of sight in a moment, leaving Silver to arrange the party, and I believe it was a good reason, that he went out of sight, I would of done the same thing.