Invest your money in S&P500 is safe because it will certainly grow up with time and with long term investment, you will get profit. Invest money in a basket of stocks like this one, will be helpful for both risk management and profit earning opportunity. If you invest money in a single stock of a company, there is risk of losing money, even all of your initial capital if that company has a bankruptcy for example.

There is no doubt about gold that is a very traditional investment asset, store of value, with very long history of existence and success. It's not bad to have gold in your basket of investment assets as it gives safety for your capital as well as chance of getting profit. However, if people want something more, with better ROI, they will look for something like Bitcoin.

In coming years and cycles, Bitcoin ROI will become smaller but it's reasonable because with bigger market cap, Bitcoin won't be able to have very high ROIs like it had in the past.

It is interesting to watch Bitcoin growth and rank climb in the future in comparison and ranking table with the other assets.
https://companiesmarketcap.com/assets-by-market-cap/

It's already happening. Just look at the last bull cycle. Bitcoin only went 80% above its previous ATH, while the previous cycles had much bigger gains. I wouldn't be surprised if that keeps shrinking next cycle.

Iirc bitcoin once climbed to #5 at around $2.2T market cap, even ahead of Amazon, Alphabet, Meta, Tesla...There was even some thread about it, and I was pretty confident it'd make it to 2 in the next bull run. But look at how NVDA and the rest of big tech are performing. I don't see it climbing to 2 in the next few years tbh.