Nothing is too big to fail in crypto world, Terra Luna is a big example that the safety of your money isn't guaranteed even if you invest in top altcoins out there, it's the same risk involve with crypto generally including BTC but BTC is just way safer, I have seen people losing 6 figures to Luna and some Defi projects, first of all try to understand what you are going into, many don't know how risky crypto space is, take risks with what you are ready to throw away.
There were projects that have become big also before but you can't see them anymore if you find them. A lot of projects have made themselves popular during this pandemic and then a lot have fallen to their rankings. With bitcoin, it's still the best and if not safe for the others, it's still the most trustworthy crypto that anyone can invest with. Yet many don't like to buy it and chooses their path to altcoins because they're looking for better and quicker gains whilst for bitcoin, it's steady and slowly.