The blockchain of each coin has a history of the difficulty target on each block. That that should -more or less- reflect the hashing power put on each coin. Difficulty is not perfect beacuse it takes some time to adjust to the variations on actual hashrate, but it's the best data there is.

Look at multipools to see how miners switch coins automatically.
You may also want to look at reward halvings to see effects in price and hashrate.

But if you want to understand the markets, you are doomed. It's just gambling. Sometimes manipulated, sometimes random, but always gambling shit.