Investors who invest for a short period buy a large amount of Bitcoin at once. Most of us are investors who don't have extra funds so they opt for long-term investments. Because in this long-term investment, we can buy bitcoins and deposit them in the investment portfolio at any time using funds according to our ability.
Moreover, long-term investment has a higher chance of profit because investors make their investment long-term, some four years, six years even many who prolong their investment up to 10 years. Bitcoins fall in price, but recover by rising again. As we've seen Bitcoin's price rise from around $40,000 to an all-time high this year. So those who patiently hold their investments for long term reach the pinnacle of success.
It's not entirely true, lump summing is not for short term investment, it's to accumulate more stashes of Bitcoin at a time, most investors who've good finances and decide to engage in Bitcoin accumulation lump sum and then possibly follow up with DCA to further expand their portfolios.
Some investors lump sum, and are comfortable with their accumulated quantity, they send it to cold storage or decentralized wallets and starts holding for as long as they wish, some still lump sum and follow up with DCA to accumulate more, while some ignorantly buys and takes away short term profits. I still know some friends that bought little quantity and rushed to cash it in when they observed little profits and I call them Bitcoin gamblers and not investors. I've seen a friend who bought Bitcoin worth of $5k in 2015 and he has not bought any other. But he continues holding and he's happy his investment continues appreciating .
There's no criteria of people who engage in short term investment, it's just about making the right decision and having the patience and composure to hold for a long time for your investment tho get very profitable.