Yes, democracy is subject to a 51% attack, like blockchain stuff. Better than a 1% or 10% attack though. Some countries like the US have a constitution that can only be changed by a majority >> 50%, offering additional but still not full protection. This is why I mentioned it’s also desirable to have a common value system among the citizenry. In the end, a country has to be more than just laws and voting, and at some point people have to actually get along and make it work together.

Definitely agree there, a democracy cannot function without the majority making concessions to the minority. Concessions like not changing the law to keep themselves in power forever.

Why is it considered an "attack" if the majority wants or supports it? Sounds like it would be working as intended if the majority vote to do or change something.

This is why constitutions exist, and courts to prevent breaches of those constitutions. This is why judges are often appointed, especially top ones, so that a change in government does not mean all checks and bounds are immediately gone. This is also why many countries have multiple legislative houses, so that one election cannot give unlimited power to one legislative house.

Thus it takes longer to slide into an undemocratic state, and checks and bounds are slower to change than a simple election. In essence, laws passed in such democracies becomes the will of the people over decades, not one election.

If a democracy has a will to move towards undemocratic rule, and it takes decades to get there, then really the people have failed themselves.

I live in The Netherlands, we have do not have a constitutional court and we still have a monarchy. A proposal to amend the constitution requires a simple majority in both houses of Parliament after which you have to call a general election. The general election is the only opportunity for someone outside of Parliament to stop it.

After the general election the amendment has to be voted on by both houses of Parliament again and win by a super-majority. Thus it is technically possible to disband Parliament and return all power back to the King within a year without the courts having any power to stop it.

So in case Parliament suddenly decides we should go back to an absolute monarchy, then we're only one general election away from completely dismantling democracy.