For those of you who just HAVE to have it spelled out..
While it's not answered yet, here's a relevant quote to tide you over.
Now be patient and have a little imagination..
"The time stone is beyond even my sight, but there are strange occurrences throughout the cosmos that indicate a re-ordering of our existence.
Like the planet Sakaar existing when it should not.
If I were called to look for the time stone that might be one of the places I would search."
And the Super Skrull rises from the ground of Sakaar and begins his hunts for the other stones.
As many saw at the end of Secret Wars, Reed and family are redesigning the universe. And since Reed sent the Hulk into space and he knows how important said planet is to him, chances are that's why the planet was recreated.
How is wanting a major plot question/hole to be answered "HAVE to have it spelled out"? I think it's a perfectly valid question to ask. Saakar was destroyed. Now it's not. It takes a little more than hand-waving by the writer on Twitter to fix something like that. And btw the current issue answered the question on the very last page, but I won't spoil it for anyone who hasn't read it yet.