Do you think cryptocurrency investors could lose all their money?

A few things to note:

1) Bitcoin and most cryptos are decentralised. It means you cannot shut it down, short of shutting the entire internet. Much like torrent(which by way is still actively running) which can't be shutdown.

2) Bitcoin can be traded in an exchange or OTC e.g. just meet someone to exchange your keys or go to classifieds etc. So banning will have limited effect although it will for sure crash the market.

3) Controlling 51% of all BTC nodes/hashrates. Also known as the 51% attack. Hypothetically possible but in reality an almost impossible task now due to the pervasiveness of Bitcoin. Even if this happens it doesn't mean every coin will be lost just that available coins can be double spend.

4) Bitcoin protocol is substantially changed, just like the 51% protocol it is a hypothetical scenario but an extremely remote possibility. Even if it happens, a new fork will be created and your coins will transfer to that new fork like how other Bitocin forks have happened over the years.

In short, like in all investments nothing is guaranteed and you can lose all your money. ​​​

To answer your question directly, yes, cryptocurrency investors could lose all their money - its not a regulated product thus should anything disastrous happen to cryptocurrency such as being banned worldwide, the value could possibly drop to 0. That being said, the possibility of it happening is really slim.

I guess something of a higher possibility that could cause investors to lose their money would be the sudden closure of online wallet sites i.e Binance, crypto.com etc. and if you didn't save your private keys, that would also equate to investors losing all their money.