Timing their collapse is the hard part. Has the bubble collapsed? Too early to say, but it is clearly leaking pretty badly.
Who benefits? The greenback, most of all. Those afraid of a dollar collapse have been hiding in gold. If fears of a dollar collapse diminish, the greenback is the clear beneficiary. US yields should fall which could temper USD strength to a modest extent.
Why are commodities losing steam? Not really sure, to be honest. One factor could be hopes that the incoming US congress will begin to get the US fiscal situation under control which should reduce the risk of future inflation and shore-up the dollar’s reserve currency status. All those factors undermine the case for commodities (and canned goods and ammunition…)