No, Bitcoin's success is not inevitable.
But --more importantly-- imagine if it WERE inevitable. Well, then: things will go pretty well for us! There's no point in discussing anything on Stacker News. We've already won. Nothing can screw us up, apparently. So just kick back and relax! In particular, you should kick back and relax, and NOT worry about the naysayers who think that Bitcoin's success is in jeopardy. ... Therefore, whether you think Bitcoin's success is inevitable or not, you should behave as though it isn't. Or you should just kind of do nothing, or go for a walk. Or take up the violin.
Humans are prone to overconfidence. Consider the famous Fall of Rome and also the sinking of the "unsinkable" Titanic. Personally, my favorite example is Star Wars Episode 1 -- if you watch behind-the-scenes footage, you see that people are afraid to contradict the great George Lucas, even though his ideas are terrible. During 2017 I noticed the same thing, particularly with taproot and Bech32 which were absolutely horrendous ideas that everyone in the community was terrified of speaking out against.
I am also fan of documentaries where people accidentally find themselves in cults, such as "behind the curve" which is about flat-earthers. They sincerely believe that flat earth will be taught alongside globe earth "any day now".
I can give you some hard examples, in fact, of the success faltering. One is the Lightning Network itself, which has become a sacred cow. It is possible to improve the LN over time, but only if experts are allowed to discuss problems -- so that we can work together to solve them. But that is exactly what is not happening (in my opinion). The brave souls working on LN have tried to discuss the "limitations" https://www.youtube.com/watch?v=BjFjK-f9ts0 https://www.youtube.com/watch?v=LnG5H62I7Ko https://www.youtube.com/watch?v=eCWTTY1eDoo https://www.youtube.com/watch?v=EocWax43QgQ . I have many LN dev friends who complain to me in private how difficult it is to accomplish this very task -- believe me or not as you will. One is an ultra-famous LN dev who actually was disinvited from a Bitcoin conference because he wanted to speak "honestly" about LN. This is debt that must be repaid with interest.
The best way to ensure Bitcoin's success is --sorry to say-- my own idea of Bip300. If the underlying blockchain software can compete fairly --without the stigma of a new coin; nor the need to traverse the political L1 dev "process"-- then we would see more innovation and less politics. Devs would compete for users. We would have had BIP 118 and 119 on a drivechain many years ago, probably 2019 at least. Which would mean eltoo and ARK would probably already be in widespread use today. In fact we would probably already be moving on to the next thing. Instead, we have to wait for the bikeshedding around covenants to stop -- that is probably 3 years away. Big mistake, and all for no benefit.