Experts can make Bitcoin related predictions but none of them will ever be entirely right. Some supposed experts thought that Bitcoin would die after the 2013 pump, but now it's smashed the ATH from then. Bitcoin price prediction is never easy, and trading is never easy. Traders might make a profit overall but they have to live with the knowledge that at any major point what they're trading could hugely collapse (especially if they're too reliant on Bitcoin) and they'll have lost most of their income.
That said, as long as traders have a few different things that they're trading and have some savings in case the worst happens, it's fine that it's an unpredictable job because it's still very profitable.
Trading is hard, there are more unsuccessful traders than there are successful ones, but more often than not, traders fail not because their ideas are wrong, but because they became too emotional in the process, this failure comes from making the wrong decisions like closing trades too early or letting their losses run too far, but never the less every trade no matter how certain you are its outcome is simply and educated guess, nothing is certain in trading.