Bitcoin investment is not like Ponzi scheme or other shitcoins that pump and dump or that will crash down rather the price will only drop and the drop of price shouldn't be a new thing or a thing of surprise to any Bitcoin investor unless you are trader that will panic and sell when the price drop.
Bitcoin investment is not risk free so saying that there is risk when an investor lump sum is what i don't get there is nothing wrong when an investor chooses lump sum it's also a strategy of buying Bitcoin in bulk at once since the money is available instead of accumulating it gradually which you can also be doing with the DCA strategy.
You've explained well. Many Newbies Confuse Bitcoin with a ponzi scheme or short-lived altcoin pumps when in reality Bitcoin is fundamentally stronger and different because it's as we all know decentralized and moreover it's Scarce which increases its value significantly and also has proven itself for almost 2 decades. Price volatility is part of its nature and anyone who expects only a straight pump will be left disappointed.
On the point of investment strategy there is no specific strategy to become profitable. You can either do DCA or Lump sum it's entirely up to you. If you want more exposure earlier then lump sum is a better , and while DCA smoothens volatility out and removes emotions of timing the market. The most important part is conviction and the ability to hold around dumps without panic selling. In the end it's not about DCA or Lump sum but about your ability to hold it long enough so you experience it's true potential.