Are investors investing in Bitcoin at ATH now are fools ? Is there chance of major correction from here as prices have already peaked now.
Does people who invested in 2017 ATH fools? Or the ones that did it two years ago fools?
Basically everyone invested in Bitcoin at the time of the current ATH made profit since they could sell Bitcoin more than the price they bought it for.
Bitcoin drove all the market up and many cryptocurrencies made a record price which is good for everyone

I agree with what you said. Investing in bitcoin during ATH is not stupid, look at the history of bitcoin over time, do they look stupid, do they regret not buying bitcoin at that time or regret selling bitcoin at that time. This also applies at the moment, btc in the last few days has just formed a new ATH, but many people predict bitcoin will continue to increase as the bitcoin halving period approaches. Currently the halving has not happened, bitcoin has formed a new ATH, of course the real ATH has not been reached, so don't ever say buying bitcoin now is a stupid act, in fact they are preparing for a better future, unless you doubt the future of bitcoin.