Buying now is a wiser decision than panicking to sell.
There are many investors who have already sold, some tagged the halving as a scam. Weak hands that could not wait longer because they are not emotionally strong to handle their investment performing in a way that they did not expect.
It is only the few that know an opportunity when they see one that will recognize this opportunity to buy some more that this dip has provided.
The reason someone would go ahead to sell their coin after the halving and even tagging the halving as scam is simply ignorance. I've come to understand that many investors came into the crypto market without first acquiring the necessary knowledge and information about what they're investing on.
They've heard hypes about the halving, about how bitcoin price is gonna break through its current ATH and be in greens, and so some start buying aggressively with the hopes of making crazy ass profits immediately after the halving and then when the market started dipping which is actually in contradiction with their expectations, they become frustrated and then start selling or blaming the people who introduced them to bitcoin.