I think you answered your own question. It wasn’t good. Apple isn’t willing to sacrifice battery life since it has been one of their biggest selling points on the iPhone for years. As far as why they haven’t figured it out yet. It is probably pretty difficult. Intel spent tons of money on it and couldn’t succeed. A chip maker gave up. That should tell you how difficult the process is. The 5G modem industry is basically a monopoly so there are a ton of companies that would be trying if it were easy to do.