i think it was a late call from RBR to switch from ultra soft to super soft. I'm sure they had the ultra's ready, but then made the late late cal.
Anyway he still had some opportunities to pass and locked up several times ruining his tires at the end.
Plus if he kept a cool head he might have had an opportunity in the last couple of laps as Hamilton said his tires were on the cliff at the end...plus the rain.

Now he probably feels how Hamilton felt last year. up by 30 seconds and finishing 3rd due to a pathetic pit call