Tbh, if you can convince someone to take your relatively worthless pieces of paper in exchange for your valuable asset, then your worthless pieces of paper are no longer worthless.
Not much different than me having a bit of cash and putting 5% or 20% down to buy a home or car: now I’m a big asset and debt holder and you got some pieces of paper with dead presidents on it.
That was the hard part of the deal: will (enough) eBay shareholders want to be GameStop shareholders.
eBay shareholders would be right to be upset with eBay management. eBay has treaded water in a niche of online shopping while online shopping has grown massively. Whether GameStop is their solution or not, Iunno.