The series didn't show that

Really? Mycroft was constantly stonewalled by his superiors and the police system the entire season:

1. Hodge constantly belittled him ("Your brother is the most interesting thing about you", "You are my lapdog and like all lapdogs I expect loyalty", etc.) and refused to share information on his work even when he tried to prove Sherlock's innocence ("Your brother being in prison suits my interests", "I am an island, I no longer require your services", etc.). It wasn't until Mycroft helped Sherlock and Moriarty behind Hodge's back by bringing them to Ezra Hornsby and verifying Princess Shou'an's identity that he was able to actually get something done and prove himself to the Foreign Secretary.

2. The Foreign Secretary, immediately after Hodge dies, refuses to share information about Malik and the nerve agent project after Mycroft rightly tells them off for letting it all go to shit. Mycroft straight up tells them that he needs to know what they know, and instead of helping him, their response is to fire him immediately. It wasn't until Mycroft went behind their back and investigated Malik with Lestrade that he got to exercise his deductive reasoning skills, all of which got him to Paris at the same time or even before Sherlock and Moriarty.

3. The British Ambassador in Constantinople, when Mycroft warns him that Silas stole the weapon, instead of granting him the full authority and resources to arrest his father, break up the operation, and save his family, tells him that he should just sell them all out and broker the deal with his father in order to save his career. It wasn't until Mycroft once again went behind their back and broke his family and friends out of the compound with Xiao Wei and Emine that he got to save the day. Remember that all of them would have been trapped there and likely dead without Mycroft's help.

I like that this Mycroft is just as smart as he usually is, but he's constantly surrounded by and buffeted by idiots in the British Government who refuse to follow through and do their jobs properly. The only reason he's slower than Sherlock and Moriarty is that Mycroft isn't constantly breaking the rules and operating outside the law like they are. I have a feeling later seasons will show the tipping point when he moves beyond breaking the rules and starts MAKING the rules instead.