Truthfully you’ll never know other than they didn’t see fit to admit you in this round and want to compare you vs the rest.
You weren’t rejected so you have another shot.
Send in mid year grades, new accomplishments and make sure you have targets and safeties. Get jazzed about somewhere else because that’s the reality for most Ivy applicants. So you need to prepare.
But the deferral does not mean you will not get in. That would have just been a denial.
Here’s an old chain where you might find a bigger or two of helpful info.