Heat offered Wade two years, $40M but he wanted either a longer deal or more than $20M/yr. Heat wouldn't go for that so he took the Bulls offer of two years, $47M.
Sources: Heat offer Wade 2-year, $40M contract
Both sides were at fault for the break-up and it hasn't gone too well for either one of them since. Wade's last 1.5 years have mostly been a disaster. Maybe not so much on the court but definitely off of it. The Heat avoided overpaying an aging Wade but then they went and overpaid T. Johnson, J. Johnson, and Waiters so they screwed up their cap anyways.