If this were to ever happen they just flip Nylander. Why would they sign Nylander long term but not Meier?

I think Meier was drawn to playing for a contender asap and management was still a year away from next year where they have boat loads of cap space and could really turn it around quick potentially, and Meier ofc wanted to be with fellow countryman/friend Hischier. Devils were always a perfect fit for him and management wanted to create that cap space for the time being while more importantly also getting their assets in return, so in this scenario, in the grand scheme of things which they could have planned, they'd have assets for Meier (Musty, Zetterland, Mukhamadullin, 2024 1st/2nd, cap space for the time being) as well as Nylander instead of just Meier.

Also, I'm not sure I'd have been as comfortable giving Meier the long-term extension for that amount of cap/years over Nylander from a management perspective as well. I think Nylander holds up better than Meier who plays a heavier checking game. Part of the sell to Nylander could be that they're also interested in competing soon and making a run at Lindholm or even Matthews as well in free agency, with many of Eklund Smith Musty Bystedt Mukhamadullin Gushchin Thrun Pulli as young guns who'll also be able to help the team win as early as next year as supporting casts (hopefully Eklund will be further along than those guys as a key lynchpin like Nylander).