All you need to know about Xcom2 is in the tutorial.
You failed in Xcom1 but, for some reason, the aliens think you are Napoleon and Patton rolled into one.
Bradford shows up carrying a neat rifle that you will never see again. He won't even lend it out to your teams, he's selfish.
Bradford messes up your rescue by not giving all his team grenades. 4 guards at the door, all in blast radius, tutorial tells you to shoot one with a rifle. That's why Bradford wants you back so bad, he's not good on details, like "Everyone got grenades? Cool!" Only you think like that for some reason.
But the one thing people REALLY need to know about Xcom2 is that it is better than Xcom1, and that wasn't all that hard to be.