How exactly do you “invest” in an offensive line in one year? What if the horses aren’t there? Should they just go out and sign a bunch of no names or someone they think can be a stop gap? Rome wasn’t built in a day.
Signing professional athletes to contracts is a game of Russian Roulette. If you wait another year, and he has another monster year next year, his price tag increases exponentially. Then again, if he has a terrible year, you might wait another year to sign him, then he has a big year going into free agency and decides to sign elsewhere for gigantic money. This was a preemptive strike by the Steelers to lock up a top flight QB for what is widely considered (at least from what I have read on si.com and espn.com) as a fair market value for his abilities.
And how do you know whether or not the Steelers included any sort of dangerous activities clauses in his contract? Maybe they did? But, then again you obviously must have read the contract before it went off to the NFLPA and NFL offices for approval, so I won’t dare challenge your thought.