Welcome to the site, you didn't do any thing wrong but without the cook details its hard to guess , if you cooked to long that's 1 reason, if you wrapped and added liquid it steamed it, watching the temps the last 10-15 degree is tough without a accurate remote therm, I don't normally wrap but wrapping works well for a lot of folks trying to get moist tender meat, all meat is different and there are a lot of variables, bet it was still great eating though,