I am not aware of any comprehensive, strong cases for why bitcoin could fail and haven't written one yet myself, so I'll at least give myself a running start here. Some of this has been mentioned by others on this thread already so consider this reinforcement of their arguments :)

I consider there to be two main failure modes for bitcoin:

Failure mode (1) could happen a few ways. But before digging into this, it's worth defining what I mean by "full potential". I consider bitcoin's "full potential" to be: anyone who wants to use bitcoin as p2p electronic cash (self-custodial electronic money with strong censorship resistance and strong security against double-spending) is able to use it, and use it at a cost that makes sense (i.e. it shouldn't cost 50 sats to spend 100 sats).

One way bitcoin could fail to reach its full potential is that the bitcoin community fails to invent and implement ways to scale bitcoin so it can be used by everyone who could possibly want to use it. Self-custodial transaction capacity maxes out and most people will end up using some kind of custodial system to transact in "BTC", reintroducing the problem of trust and reversible payments that bitcoin was designed to solve in the first place.

Another way bitcoin could fail to reach its full potential is that the bitcoin community fails to invent and implement ways for BTC to be used in every type of transaction where money is required. For example, many new privacy protocols, p2p financial contracts, and self-custody schemes such as vaults have been implemented on alternative blockchains. If someone wants to use these new features with their money, currently the only way to use these features with bitcoin is using (semi)custodial mechanisms for bridging bitcoin to these other chains (RBTC, L-BTC, WBTC, and the like), again reintroducing the problem of trust that bitcoin was designed to solve. If people want to use these new features in a self-custodial way, they have to buy an asset that is native to these other chains that implement the feature (ETH on Ethereum, for example). If people continue to buy these alternative assets instead of BTC because BTC cannot be used with these new features without some (semi)custodial mechanism, I consider that a failure of BTC to reach its full potential.

Maybe my definition of "full potential" is a mirage and can never be obtained. I'm willing to accept that, provided all options are exhausted. But I do think it's a goal worth striving for.

That brings me to failure mode (2), nearly completely failing. There are a couple of ways failure mode (2) could happen that I can think of.

The first is as a conclusion of failure mode (1): because bitcoin fails to reach its full potential, eventually enough "true believers" die off that more and more BTC left to the next generation is sold, fewer and fewer people are transacting and paying fees to miners, etc. So there's this "death spiral" feedback loop of fewer users -> sell pressure and less usage -> hashrate drops -> less security -> sell pressure and less usage -> hashrate drops... etc and this continues until bitcoin is basically a hobbyist thing that maybe a few thousand people worldwide care about and the market cap is at most today's equivalent of a few million USD. As long as there's a single computer mining blocks, bitcoin will never "completely fail" in terms of totally stop working, but as a monetary system, for all intents and purposes, if it is a hobbyist thing used by a few thousand people at most, I consider this "nearly completely failing".

Another way failure mode (2) could happen could be instigated by a severe govt crackdown: bans on self-custody, exchanges, mining, running nodes, etc. This could leave a core of "resistance fighters" who continue to use bitcoin underground. They will need to "keep the flame alive" by recruiting the next generation of resistance fighters, if they don't maintain sufficient recruitment then the "death spiral" I described above could occur as the resistance fighters die off.

There is a failure failure mode (3) which I consider highly unlikely but worth mentioning. This is "total failure" meaning that no more blocks are mined and bitcoin has zero monetary value because it cannot be transferred and/or literally everyone has lost interest in bitcoin. For this scenario to occur, computers and telecommunications networks will need to completely fail for an extended period of time. This is a post-apocalypse scenario: nuclear war, asteroid strike, a cosmic event fries all computers including miners, the sun explodes before humans can get beyond its blast area, etc.