It's entirely possible that they're an individual investor without any affiliation to the "whales." Thus, only the owner knows when and why they're selling their BTC.

Wow, do you think there will be 'many people will buy and the price will rise again'?

It's hard to say for sure, as the existence of Bitcoin will remain decentralized from now on. This makes it a highly speculative investment, subject to each individual's strategy, facts, and opinions. While many people may be tempted to buy Bitcoin after a wallet dump, this can also cause panic, leading some to sell their Bitcoin. It's important to remember that everyone has different levels of resilience and patience. Therefore, mere confidence alone cannot predict a significant surge in Bitcoin purchases after a dump.