Even in the US, which is first to file, your patent can be invalidated by published prior art that makes it obvious. The stuff made here video is a textbook example of an invalidating piece of prior art.
I assume they are going for a design patent, which they may well get (and doesn't protect against much other than direct copies). A method patent or a utility patent is a lot harder in light of the prior art.
The problem is that the patent system tends to just approve anything that meets a certain quality threshold. And then they leave it up to the courts to adjudicate whether a patent is invalidated due to prior act.
And so rather than litigate, roll the dice and potentially strengthen the patent's standing sometimes it's easier just to negotiate a deal with them.
Yes, it costs money to get a patent invalidated based on prior art. But: an amount that even a single person who stands to actually gain from having a patent overturned should have no problem with. You're asking the USPO to spend time redoing work, literally halting any other patent work they could be doing instead. So it's not a trivial amount, but it's also hardly a prohibitive amount if you actually want a specific patent revoked.
The AIPLA Report of the Economic Survey for 2017 notes that the typical patent infringement suit with less than $1 million at stake costs on average costs more than $600,000 dollars, while the typical patent infringement suit with between $1-10 million at stake costs on average nearly $1.5 million to litigate.
