The beauty of Bitcoin is long term investment. Hodl until it turns green. If it is not green, it isn't ripe for harvest. Each time a red candle appears, it is a signal to look out for buying opportunities.
I still don't understand why people invest in Bitcoin for short term and not long term, haven't they learnt from history that Bitcoin always reward it's hodlers and those who sell early always end up regretting. As an investor hoping to benefits in this market, we should learn to do our research on the history of Bitcoin before investing so we know what we're getting ourselves into.
Most of these investors doesn't really know what they are doing. Most of these short-term investors are newbies that were influenced by other people or circumstances and get hyped because they see people gaining profit in a short term. So they use the money that they can't afford to lose, that is why most of these investors often sell when they see profit, or when the market is crashing.
Some investors see red candles as selling opportunity when what they should be doing is observing as you said to see if the market will give them a very good discount with price drop of the market. As an investor your target should be that when it's about time you exit the market, you can do so comfortably without caring about the state of the market (don't care if it's a green or red candle) because you are in profit no matter the situation of the market, that should be your goals as an investor and not investing short term.
They panic sells because the trend of the market is not what they had expected. Having weak hands, they immediately sell to cut more losses when the candle turns red. Some investors short their trade thinking that the price will go lower to buy more Bitcoin.