I agree with the title, but I don't agree with why no one understands the 51% attack.

Too many people think that the method of 51% attacks is detectable while it's in progress because of how it's described in the Bitcoin whitepaper.

The actual method that nearly all successful 51% attacks on PoW networks have occurred is via withholding attacks, which are undetectable until the moment they execute.

One moment the blockchain is safe; the next second, 50 blocks are reorged all at once and it takes a whole day for honest miners to fight back, assuming they can even muster the mining power to do so.