The question is who asked for it? Did the Bitcoin developer ask for Charles to make it for them?

And what benefits will Bitcoin with Cardano being as second layer? Staking? Yielding? This is really hard to watch to be honest.

When you see an altcoin project that tries to by whatsoever way, to bind their project with Bitcoin in technology or only in part of a coin name, it's like a hook to steal your money.

Because there is no other best way to attract potential investors and gamblers than using something related to Bitcoin, technically or namely.

Bitcoin forks are simply altcoins, but their names need to have the word Bitcoin.

Cardano tries to make noise, attract people with their money to Cardano with this idea and video.

Bitcoin layer 2, side chain?
Sidechain Observer - Bitcoin L2 Projects & current state of development

Altcoins like Bitcoin forks need Bitcoin source code for forking, and they need Bitcoin in their names to increase their chance to successfully scam investors.

Altcoins like Cardano want to use Bitcoin as their tool to scam Bitcoin investors and convince them converting their valuable bitcoins to useless altcoins.
Altcoins like Ordinals, Runes want to use Bitcoin blockchain for their scam NFTs and tokens.

It's easy to see why they want to be parasites of Bitcoin blockchain, as it helps them increasing successful chance.

Cardano cannot solve the problems Bitcoin is solving as it's remains just another layer 2 blockchain based project just like others. With subsequent time, they integrated more features on their blockchain that solves the problem of decentralization finance, staking, lending, on their respective Dex.

There has never been a platform using Bitcoin for all these features that's why you never see any coin built under Bitcoin network performing the function of decentralising finance, and the rest. This project Mintlayer is trying to solve this problem but they been struggling with it for many years.

We really don't need another layer for bitcoin. But who knows, there will be changes or developments in the future that we may really need it. For now, we now that btc network can withstand on its own without other networks on top of that for security purposes.
ADA network is managed by cardano foundation. Of course, they will surely favor their foundation when it comes to decision making. But with btc network alone, there won't be no inclination as to whether they will favor this network or not. I still prefer btc to stand on its own without the intervention of other networks.

There is a problem with your post, you probably thought that you pasted the needed part inside, but it isn't there..

I think the initial idea is for them to do it in a decentralised way using this -> https://bitvm.org/bitvm_bridge.pdf. Individual UTXOs are locked up on Bitcoin and is up to user's discretion when to unlock. On Cardano, users get a wrapped Cardano native asset in respect of the locked bitcoin. I guess the downside is the Cardano native assets are not fungible but they can be staked or swapped entirely.

Seems not terrible, but I don't think people would run in to use these "defi" capabilities still.
Especially those who know the value of their BTC and keys for it.

Absolutely not, I don’t support Bitcoin having anything to do with Cardano which is essentially a centralised shitcoin. I’m sure it works for Hoskinson but no thanks, we don’t want any individuals that mostly control a particular asset having anything to do with Bitcoin. 

The Cardano "layer 2" was, as far as I remember, meant to use the BitcoinOS/Grail bridge. According to their whitepaper it is a dynamic federation using ZK proofs to determine the validity of peg-ins and peg-outs.

From a first glance, I consider this one of the better bridge/sidechain models, however I haven't analyzed it in detail. If I see positive feedback on Bitcoin blogs for sure I'll analyze it. But for now I dislike the marketing language, technobabble and namedropping (of course, it had to begin with "Satoshi created Bitcoin in 2009 blah blah" ...) in the whitepaper and on their website, and several similar models have also been implemented already, in particular Nomic and Threshold Network's tBTC.

But in general I'm not opposed to use a "second tier" altcoin like Cardano as a Bitcoin sidechain; as Cardano sees low usage natively, it can potentially provide cheap "pegged Bitcoin" transactions. The big advantage is that these altcoins already have a proven staking mechanism and their security budget is high enough to lock/unlock some BTC worth of value on their chain.

The fundamental problems of PoS, which is still inferior to PoW, however remain. Thus, I'd like even more to see PoW altcoins like LTC, Doge, Dash or Ravencoin (Monero isn't suited due to its non-existing scripting capability) as Bitcoin sidechains.