What did they want him to do for them? Crawl under their blankets to warm them up? Boil some water for them? He's not even a part of the state's executive branch. Realistically, all a senator can do in such a situation is to pay some lip service, which can be done from anywhere.
This type of shit is annoying for both sides of the isle. Is it a requirement to no longer travel when you hold public office? I haven't been watching the news, but either way Cruz is a federally appointed official. Not much he can do with the Texas situation. Kind of up to the state to figure it out and then request an emergency declaration, which has nothing to do with Senators.
‘My family freezing, my senator is in Cancun’: Twitter explodes as Ted Cruz accused of traveling out of storm-hit Texas'
https://www.rt.com/usa/515908-ted-cruz-anger-travel-storm/