A little known fact is that Wizards did actually “officially” distribute these Pikachu promos via one of the US Illustration contests.
I interviewed one of the winners (Wayne) a while back and he confirmed he received 10 copies of 1st Edition promo Pikachu for winning: pokumon.com/article/wizards-illustration-contests/
It’s likely that these were leftover prints from their intended (but botched) distribution so Wizards was looking to offload their stock.