Security online depends predominantly on logging and auditing.
Twitter has extensive logs of user actions, so maybe, but it would have been much harder.
But all of these, given enough attacker motivation, can be subverted. For most users, it's sadly not that hard.
Stop thinking of locked down Fort Knox and unbreakable encryption. Start thinking of tedious accounting & logging.
So now, voting. Why is voting online so impossibly hard?
And yes, in fact, you can. See @heliosvoting, Microsoft ElectionVault, and all of the prior work on e2e-verifiable voting.
Because security depends on logging. And voting, by design, throws away the logs.