Investing in the DCA method is safer~~~
DCA method isn't about safety but about the quantity of discretionary income at your disposal as an investor. If you've a large discretionary income available at the point you want to invest, then you can go ahead and lump sum and it's still financially safe. DCA provides a slow and steady approach to investing into Bitcoin and even when using DCA, if you're over aggressive in DCAing, you would not be too safe as you may not able to sustain it for long.
Investors who use the DCA method more aggressively are usually those with a substantial base income, perhaps even more than their daily needs. Therefore, if such an investor wants to use the DCA method more aggressively to buy Bitcoin, I don't think it would be a problem for them, as it depends on their financial capabilities and their desire to own a large amount of Bitcoin in a relatively short time. Therefore, we must consider the person implementing the strategy so that we don't assume everything is the same for everyone. The way people with a large income and those with a modest income will certainly differ greatly in their approach to investment methods, including the DCA method you're discussing.