So why did Bitcoin just disappear all of a sudden? And how much power do I actually need to make some money
Bitcoin didn't disappear. It is still out there, producing new coins, worth $381 per bitcoin. The problem is there is so much processing power that to mine a $381 bitcoin today on a GPU, it would take probably on the order of a few thousand dollars worth of electricity.
To be able to mine it profitably, as in getting more bitcoins than it costs in electricity to produce them, you need to use ASICs, or Application Specific Integrated Circuits. They are machines made with custom built chips that only generate hashes for the SHA256 algorithm. For an example, a 280X/7970 AMD GPU will generate about 700 million hashes a second. An Antminer S3 sells for about $400, so it is in the ballpark for the price of a 280X, just a bit more expensive. The Antminer S3 gets 441,000 million hashes per second.
That is 630 TIMES the hashing power of a GPU.
A Zeus V3 gets 4,500,000 million hases per second for about $4500.
The problem is that while the processing power keeps increasing, the number of coins generated do no. So as the overall hashing keeps increasing, your share of the pie keeps getting smaller. Eventually, what you get doesn't pay for the electricity used to produce it, and your ASIC becomes a space heater. The newer ASICs are that much more powerful, and people keep designing new ones. Plus several companies designed them, got the value out of them, then sold them to people who weren't able to get back a positive return on their investment. So people are really hesitant to plunk down $5000, or $10,000 or more on an ASIC that may never pay for itself.
Currently that Zeusminer will earn about $21 a day, and cost about $7 a day to run. Profit of $14 a day. That means, if the difficulty (amount of hashing power on the bitcoin network) never went up, it would take 321 days to pay for itself. But we haven't reached the top of the curve. Difficulty keeps going up, and as it does, you make less per day. It may never pay for itself.
The best I'm seeing on this page:
https://en.bitcoin.it/wiki/Mining_hardware_comparison
Is the Achilles Labs AM-6000, that has a hash power of 6,000,000 Mh/s or 6000 Gh/s for $2895, and it pulls 3800 watts. It will take 150 days to break even at current difficulty. That may be doable.
This link will show you the total hashing power being dedicated to the mining of bitcoins:
https://blockchain.info/charts/hash-rate
It is right now around 300,000,000,000 Mh/s.
Is this helping you understand?