It is certainly very possible to earn in bear markets, provided you use the right strategy at the right time, namely short selling. Since this thread was started in 2018 more and more trading platforms are cropping up to either increase their leverage allowance (okex went from 2x to 5x) or to incorporate margin trading for the first time (binance introducing it soon). Then there's bitmex who has dominated the field for the last few years with 100x and primexbt who launched early this year to also offer 100x and is incredibly popular for such a young exchange.   

The growing trend has much to do with the demand of traders wishing to short sell and earn in both rising AND falling markets.  While it is inherently a riskier way of trading you can invest less capital at the same time by increasing the position size with leverage. They key is to understand the risk if you wish you enjoy the augmented reward.

Alternate strategies include: simply buying more while the price is low (provided you feel the market will correct and hopefully go much higher), futures, binary options, and as mentioned (and by far the most popular method) is shorting by margin trading.