Currently we have a classic market race - the market forces both companies to provide more and more capable models with more and more value for the money for the customers while the suppliers (Nvidia, Micron, Dell) squeeze them from the other side. The end result would be one winner taking it all (and that is a very humongous "all") while the other falling into a very distant second position at best. Do their leadership and investors (bonus points - look at some OpenAI investors), some already worth tens of billions on paper, like the prospects of that "50% chances of even more riches, 50% - bust" outcome? I'd think - no.
The outcome they would like is both companies divvying up that huge market while jointly raising prices and providing less capable models (ie. cheaper to train and run) while squeezing their suppliers Wallmart style. How to get there? By breaking the anti-cartel limitations.
The typical tools to break anti-cartel limitations is for example perception of national interests or perception of some imminent dire emergency.
Thus the "lets us collaborate or our AI will kill you all" scare campaign.