For those who want to diversify in their investment, bear market is the perfect time to do that, because bear market helps to flush out scams, and weak projects since we have thousands of fake projects like shitcoins, bear market eliminates them all, and only real projects survive like BTC.
If you want to diversify, you don't need to diversify into investment of the same line i.e since you are a bitcoin investor it doesn't make sense to diversify into shitcoins because bitcoin price movement controls the market and bitcoin is their king. If you diversify into shitcoins when the market is down, all your investment will depreciate and you will be in big loss. The reason for diversifying is to preserve your wealth so that if one is at loss, the other might be in profit to balance it up. If you want to diversify, you can diversify into gold, landed properties and cash equivalents.
When investor of bitcoin want to talk about diversification of their investment, first mistake is to think that by buying an altcoins you are diversifying, well that not, is better to move away from cryptocurrency entirely when you already have bitcoin in your portfolio, and you are considering diversification.
We have other investment models that are traditional assets but still make a perfect choice for alternative investment to your bitcoin: buying stock assets or going into real estate properties, gold, as you mention; all these are good and tangible ways of diversification.