That's what they are doing. The "charge what they want" isn't a bunch of execs going "I know, we'll charge £6k next increase, we'll all make loads!"
The cap is set based on the cost to serve the average user. It covers the cost of buying the electricity units and amount of gas, the cost of running bulb and other failed suppliers (because the cap before want high enough for them to survive), policy costs like the green levy's, profit which is about 2% and why they exist in the first place, and the network costs of getting the supply to you in the first place, and maintaining that supply. Easy for those profits to be wiped out if people use more than expected and tbey need to buy extra energy to cover but price has rocketed. The cap exists to stop them saying it'll be £8k for the svr and making 30% profit margins. Running at a 1.9% profit margin is wafer thin. When people say freeze the cap etc, need to consider how that will be paid for because that delta will need funding - they'll still have to buy the energy at market rates so if they can't bill you for it, who pays? The treasury? Plus there will then be a number of people trying to control bills who have taken the fix like you have mentioned, so would then be locked into an expensive deal with exit fees of £300 or so to get out so how do you support them?
You're looking at a fix so what you're seeing is the likely realistic cost at current prices to allow them to buy ahead based in your usage, and gamble that there will be more increases to make it worth locking in. Your other option is to remain on svr which will be initially a lot lower than that but who knows which direction it will go in?
It's crap and I've no idea how lower income people are flint to survive it, something needs doing but needs some fresh ideas. Or a huge pot of cash.