What we don't know if is the Indians or Red Sox were willing to give Santana four years, or if it was entirely about the dollar figure, but the key moment was still him agreeing to take a three-year deal (while being rewarded handsomely for doing do).
Would Darvish take four? I dunno, but he started the FA period as the top guy and if anything he is even hotter now (because the guys with QOs,or at least, Cobb, are asking for the same level of deal, so why not sign the one with no QO who might also be better, albeit also older. His WS performance is largely irrelevant, even if it hasn't turned out he was tipping.
Anyway, it was easier for the Phillies to overpay someone who wasn't the top guy, they wouldn't have been able to do that with Martinez or Hosmer. If they're not scared of the losing another pick they can probably make a move but I don't think they are going to beat the Cubs or Astros (or Rangers) for Darvish.