The premise is how do you know that this altcoin will crash, if this altcoin crashes no one will continue to buy it, you can only choose to short. If this altcoin does not crash, but has an upward trend, then it will be very dangerous for you to short, and the risk of investment definitely exists. This will test your insight into the market.
There are ways to know this. The main one would be if this was a poorly built altcoin and then it looks suspicious. It's crazy but when some shady alts crash, there are still people who invest on them especially if they are famous because they still expect that it will recover. If the altcoin continues to rise then isn't that great?
It means we can sell for a juicy profit but it's not only advisable to buy during those moments, only to be safe from the bull traps. Wealth are created during the bear seasons or whenever the coin collapses but it must be accompanied with a proper research so that we are sure that the alts that we will pick can still be able to recover.