Actually don't think these are that bad.

Why would the islanders make that trade?

Best guess is:
1. Roster player to replace Mayfield's spot.

2. an RFA RHD who I was wondering if Jordan Gross (same age RHD but a point per game in the AHL which could translate in the coming years) was a better choice but that contract is UFA and my guess was a guaranteed hold in the RFA contract was better.

3. The 3rd round pick is a slightly lower than average value for a stay at home, physical, mid-pairing Dman, but since they already have the Avs 2nd, I was hoping a roster player and some type of young but useful player in the same vein of the player they're trading away who has a resume that says they can challenge for a roster spot as soon as next training camp or be a main callup would help this slide.

EDIT - forgot some words
2nd EDIT - would replace McKeown with Gilbert who projects to be similar to Mayfield

Mayfields value is closer to what Savard returned last trade deadline. He’s also decent offensively, he can drive play and his shot is pretty good. He also has a reputation of being solid in the playoffs on a team that went to back to back ECF. Also you have to factor in his contract which is well below market value. The islanders won’t trade him unless they get at least a 2nd and a good prospect or a 1st straight up.

Yeah Savard wasn't worth what they got. Mayfield is a bottom pairing Dman maybe a 4th. Not much leverage for his services. I disagree with two assets plus the pick for Mayfield. I could see murray and a 4th and maybe a 6th round pick. Not certain Mayfield give Avs much that Murray doesn't.

Mayfield is not a bottom pair D man. His analytics, TOI, and reputation don’t support that. Chiarot is barely an NHL defenseman and he’ll go for a 1st at the deadline, if the isles choose to move mayfield , they will get a lot more than you proposed.

I'd pass as it stands from an Avs PoV.