Restructuring is actually very simple. It’s basically when a team converts a player’s salary into a signing bonus. For the player (and agent), this is an easy sell. They get the same amount of money except now they’re getting it in up front and it’s guaranteed.
Tom Brady and Eli Manning both restructured their contracts last year for the same reason. The Patriots, comically, went so far as to only pay Brady $950,000 in base salary last year (20x less than he's worth on the open market).