The offer sheet was negotiated into the CBA as a perk to give the players some RFA bargaining power. However, it's purely up to the GMs and owners to make offers to RFAs and because it drives up RFA salary it's not something that NHL ownership wants to do. This predatory offer sheet is an extreme case because not only are you giving Eichel more AAV than he probably otherwise gets, but you're also helping him cash in earlier because of how soon he'll hit UFA. Every GM is going to try to use RFA leverage to lock guys in for a few of their UFA years, and I doubt anyone wants to risk compromising that by making this kind of offer, especially because if the offer sheet isn't matched, you're losing 4 1st rounders and gaining a huge liability and risk.
Revenue that goes to the league and owners is locked at 50% of total revenue so increasing one player or even every player's salary figure doesn't affect the amount the owners make. However, it does effectively reduce the take home salary of every other player in the league to have one or a few players with an inflated salary figure, and would almost certainly cause a lockout to happen the next time the CBA expires. Every GM is ultimately an employee of the league and so you're not going to see any decisions that are so blatantly damaging to their collective interests.