I will eventually be running Rime of the Frostmaiden before too long but encountered something confusing when I went to go look into its lore.

Chardalyn in 2e roughly states it is a brittle, fragile stone that absorbs one spell and releases it when broken. Chardalyn studs containing fireball spells placed on a shield means a nasty surprise when the shield is struck.

Chardalyn in 5e ROTFM is contaminated with evil energy and causes Chardalyn Madness. It is used to make anything from rings to maces to even a giant dragon construct without it being brittle or possessing even a single spell. I’ve heard it’s because of the Crystal Shard, that all sources in Icewind Dale are contaminated, but this doesn’t explain why one of my players can’t destroy the Chardalyn Dragon with a single thrown rock or how a variety of weapons don’t shatter on impact. Other items that typically require durability are made with the supposed brittle material. 

Now my questions are, how can this be possible  if both are true? Or was there a lore change between editions that I can’t find reference to resolve my confusion?

Fifth edition lore supersedes all previous lore and previous edition is not required to run a fifth edition adventure. You don't need the second edition lore for Rime of the Frostmaiden and any lore you do know that contradicts what's in the adventure can be ignored in favour of what the adventure says (assuming you're running things by the book and don't want to homebrew the module to any degree)

Editions are separate.

What happened in 1st-4th edition may not have happened in 5th unless there is a 5th edition book stating so, or your DM has decided to incorporate it.

Editions are self-contained. That's why they're editions.

Or,the in world explanation, could be that blue fire of the spell plague altered it.  If you want to keep previous lore compatible, regardless of what others want to impose on you, do so and enjoy.

Quote from GodwinXZ >>

Or,the in world explanation, could be that blue fire of the spell plague altered it.  If you want to keep previous lore compatible, regardless of what others want to impose on you, do so and enjoy.

 
Nobody is imposing anything.

The question asked is about official lore between editions to make "both" versions true.

The answer is there isn't any, because not both are true, because editions are self-contained.

DMs are free to make up whatever they want to have it work however they want. This is why I said "or your DM has decided to incorporate it".

As others said, that was a different edition, things worked differently then. FWIW, Crawford said as much:

"If you're looking for what's official in the D&D roleplaying game, it's what appears in the products for the roleplaying game," Crawford said. "Basically, our stance is that if it has not appeared in a book since 2014 [the year that Dungeons & Dragons' Fifth Edition core rulebooks came out], we don't consider it canonical for the games."

Interesting. I like the thought there and it doesn’t require me to do a lot of work add some interesting elements to my campaign. Thank you.

Quote from Cyb3rM1nd >>

Quote from GodwinXZ >>

Or,the in world explanation, could be that blue fire of the spell plague altered it.  If you want to keep previous lore compatible, regardless of what others want to impose on you, do so and enjoy.

 
Nobody is imposing anything.

The question asked is about official lore between editions to make "both" versions true.

The answer is there isn't any, because not both are true, because editions are self-contained.

DMs are free to make up whatever they want to have it work however they want. This is why I said "or your DM has decided to incorporate it".

 If editions were “self-contained” then there would not be an ongoing story particularly in the Forgotten Realms.  Each edition has had an effect on the story, be it the Time of Troubles, the Spell Plague, or The Sunderings.  Until Crawford made his statement it was up to the individual DMs to decide what to use and not for their games.  His statement takes that away in all products put forth and imposes their will on gamers.  

As for the question posed, I offered a potential solution using in world passed lore that may or may be used.  

Quote from GodwinXZ >>

Quote from Cyb3rM1nd >>

Quote from GodwinXZ >>

Or,the in world explanation, could be that blue fire of the spell plague altered it.  If you want to keep previous lore compatible, regardless of what others want to impose on you, do so and enjoy.

 
Nobody is imposing anything.

The question asked is about official lore between editions to make "both" versions true.

The answer is there isn't any, because not both are true, because editions are self-contained.

DMs are free to make up whatever they want to have it work however they want. This is why I said "or your DM has decided to incorporate it".

 If editions were “self-contained” then there would not be an ongoing story particularly in the Forgotten Realms.  Each edition has had an effect on the story, be it the Time of Troubles, the Spell Plague, or The Sunderings.  Until Crawford made his statement it was up to the individual DMs to decide what to use and not for their games.  His statement takes that away in all products put forth and imposes their will on gamers.  

As for the question posed, I offered a potential solution using in world passed lore that may or may be used.  

That would only be true if the D&D police were going to raid your house for playing the way you want. Crawford’s statement was, as always, a guideline. Due in part, I’d imagine, to a desire to not force new players to feel like they had to research 40-odd years worth of often conflicting lore for a home game where most of it will be completely irrelevant. He gave an option which simplified things, he didn’t forbid anyone from doing anything. You are, as always, free to play how you like.