Normally, when I'm tracking down the cause of a price movement like this, it doesn't take very long to find a new Standard or Modern deck that's risen to the forefront, a new MTG commander that's getting fans excited, or a card coming out in the next Magic: The Gathering set that works immensely well alongside a niche old playing piece
Proliferate allows you to choose any number of counters on any number of things and add another one
And if the foretold card is an instant, you can cast it from exile as an instant (while plotted cards must be cast at sorcery speed)
Valor in Akros Valor in Akros, when paired with token producers like a Call the Coppercoats, puts huge power and toughness buffs on your team
Given the remarkable levels of hype for Magics latest and greatest core set, this has been a long time coming
and many others, no doubt