The main problem that bitcoin is facing right now, is the huge manipulation that can be done by just a little group of people. I mean, someone with a few million dollars can easily move the market upsides or downsides.
It is easier to manipulate than the other markets (like the stock market, commodities, or any other thing)
I think you are absolutely right that manipulation is common, and a huge problem. But I think with Bitcoin it takes huge sums, and coordinated efforts from teams of very knowledgeable people. But the smaller coins, even ETH, are very vulnerable. I read that for $4000 an hour you can harness enough energy to dominate ETH (51%)