Shiranui differentiates itself from the other tiered decks as Shiranui doesn't have any considerable fragility when in Side Deck format. It has also shown an impressive versatility to side for everything without affecting their consistency and that's the main reason why this deck is back to Tier 1.
Shiranui finds itself back on Tier 1 because of it's ability to adapt so well to any given meta because of the decks ability to play a large number of techs and any skill. Shiranui are doing especially well this week due to the resent rise in Crystrons (as shown in Clan Wars data) as Shiranui is one of the few decks with a favorable Crystron matchup through the usage of No Mortal Can Resist .
When a deck like Elementsabers has such easy acess to the most problematic fusions like Loading... and Loading... they get in the position of being the most hated deck when it comes to siding. As such, cards like Loading... were already being sided, but it was never enough to demote such a powerful deck to Tier 2. However, with the popularity of Loading... in the Side Deck (even being ran in the Main Deck}, Elementsaber's performance has suffered.
Elementsabers started to struggle in this current meta, since Loading... become the most played tech card, that every deck can run, without hurting their own plays. Artifact Lancea can shut down your fusion plays, unless you have the required fusion materials in your hand, but you still lose the cycle of Loading... . The rising popularity of Dark Magician and Artifact Lancea means Elementsabers are demoted to Tier 2.
Although very powerful, Elementsabers have been time and time again struggling each week to the popularity of decks running 3 Loading... in the main / side deck. Because of Lancea's prevalence in the current meta, Elementsabers have taken a large hit to their ability to end games.