Another way to look at it is that the fact that the tweet made the typo is an indication that other people are likely to make the typo, and this way they don't

Another way to look at it is that the fact that the tweet made the typo is an indication that other people are likely to make the typo, and this way they don't lose out on those users. .io is probably more memorable than .to. (It's all arbitrary, of course; they're both just unrelated ISO codes. But for whatever reason, .io has become the canonical “the .com was taken” refuge.)