It isn't really hard to
mine profitably, you can look up which ones are profitable and choose out of over 1,000 coins, of which 100 are already above market cap of $500M, so that's not the bootleneck.
As soon as a coin's value increases, more mining hash power enters the scene and difficulty shoots up (ruining your profit margin). You then swap to another coin, eventually the same thing happens. Rinse, repeat.
During all of this, you still have to make back your initial investment on the GPUs and power, then you have usually another 6-9 months max before your entire rig is too outdated and you have to start again buying newer, faster cards (which will then take you another 3-5 months just to earn back your cost).
Just seems a very painful and slow way to cash in on the crypto bonanza (which isn't going to last forever).