He's staying in CFB because he shat the bed this season and ruined his draft stock, and Miami was desperate for a QB late in the cycle (are they just going to use this strategy every year?) so they dumped a boatload of money at him, way more than he'll make as a rookie in the NFL. I'm sure it's a perk his gf goes to Miami but she wasn't the driving factor getting him there lol.
It's a good move for him; he needs to improve his draft stock and he'll definitely have an easier time against ACC defenses. Not to mention the money. I'm not so sure it's a good move for Miami from a cost-benefit perspective. Are they for sure a better team with Beck than the scraps at QB they had? Absolutely. The problem is that they're paying Beck more than Ward. Beck is no where close to Ward and they couldn't even get into the playoffs with Ward, so in the end I anticipate that they're paying millions to avoid a potential disaster of a season, but they'll be worse than they were last year.