Nintendo signs the deal.
Valve says they don't need to sign the deal they trust Microsoft.
Sony kicks and screams refuses the deal.
MS and Nintendo are not direct competitors.
Steam is the largest platform for delivering content on PC - they have built in leverage where this isn't necessary and they're not a HW manufacturer.
Sony is the odd man out and direct MS competition - any deal proposed by MS will favor them and likely include caveats, so of course there's going to be pushback.
I really don't get this weird belief some of you have were MS should face no resistance to their acquisitions. We're not talking about some small developer like Ninja Theory, we're talking about the largest publisher in this industry. We already saw what happened with ZeniMax.