I know blue will always have its moments, some games it's just great for the team, and other games you need more damage and less kiting. The damage build used to be rush triforce into more damage, and blue was tear into frozen gauntlet, but the current popular Ezreal build is tear into triforce. Why is this the current preferred play style? Why not rush triforce into more damage? Is muramana really the best late game damage item for El?
Blue ezreal is for CDR over damage.
Ezreal can use up a lot of mana, especially when he relies on Spellblade (Iceborn or Triforce) That's the main reason people take tear early. And then it's kinda obvious to continue Muramana.
Because most supports in low ELO probably don't know what the word "Peel" even means, much less how to do it effectively, they just lock 
and go front-line initiator late-game and forget about their carry.
Well with the recent nerf to the crit chance of IE you only get 30% with TF and IE which isn't really that much. People go tear because the early damage spike of manamune and TF can really do some damage in both siege scenarios and teamfights. You just poke down with the high damage of TF+muramana and it has better all-in potential than ibg but a slight bit less kite. I'd say bot lane ezreal should go TF since you might be the sole physical damage of your team but if you're mid or you have a damage top lane like jax you can opt for the ibg.
Either way IE was already a border case where it was up to the player whether or not to pick it up and the nerf made it even less viable. Muramana seems to fill the void quite nicely.
