Chart shows the price of Metapod #11 at the end of each month going back as long as we have tracked the item.
Magikarp has always been a fan-favorite Pokmon, mostly because it's relatively useless, but has the potential to evolve into one of the most powerful Gen 1 Pokmon ever, Gyarados
Higher-budget collectors have more room to target Gold Stars, key vintage holos and premium condition copies
Another common way to abuse tutoring effects on creatures is with copy effects like Spark Double, or by copying Recruiter of the Guards effect with cards like Panharmonicon
Global demand + nostalgia/resale growth : As Pokmon becomes increasingly global, high-quality Japanese variants attract collectors worldwide driving up demand and price
That strategy previously had no access to dual lands to fix its mana, but now it has 10 more to choose from (though the red-green and green-blue options are likely the most relevant to it)