Technology

LastPass's biggest problem was that they were almost the first in the game, and mistakes/choices they made 20 years ago bit them hard when they got hacked.

There were two major issues with LastPass's security model:

1. Non-Password data wasn't encrypted. So usernames and urls were visible by the people who stole the vaults.
2. Passwords were encrypted with a number of iterations based on when the account was created, so older accounts were only run through a single iteration. The iteration process makes it much harder to guess the master password(by making it take a longer time). So single iteration makes it pretty quick to guess the password.

So with flaw 1 you could see what vaults might have valuable passwords like banks and crypto wallets. And with flaw 2 you could reasonably quickly break into the vaults of long time users.

So aside from their lax security allowing the compromise to happen in the first place (Nothing is fool proof), they weren't providing the level of protection most people assumed.

More modern password managers like BitWarden fixed those problem a long time ago.