Why does anyone give much credibility to Mueller's latest indictments for Twelve Russian military intelligence officers in Hacking probe?

Politico's headline questions the timing of Mueller's indictment of Russian military intelligence officers just one business day before Trump is to meet with Putin (‘It's a big FU from Mueller’). But put aside the timing of the recent indictments, does anyone remember the Mueller probe's previous indictments of Russians regarding their interference in our election? How they had indicted Russians in the belief that they wouldn't contest the charges and when the Russians fought back, Mueller suddenly had to ask for delays in the proceedings? From the WSJ in May:

In February, in its first indictment based on alleged conduct directly related to Russian involvement in the 2016 campaign, Mr. Mueller’s office charged three Russian companies and 13 Russian citizens with engaging in a widespread effort to interfere in the presidential election. . . . 

Mr. Mueller’s prosecutors accused them of funding efforts at another organization, the Internet Research Agency LLC, to create fictitious online personas and set up hundreds of social-media accounts—on Facebook , Twitter and Instagram—that pushed divisive messages and helped organize rallies in advance of the November 2016 election. . . . 

Mr. Mueller’s office asked the court to delay Concord Management’s arraignment, in which the company would enter a plea, saying it had tried unsuccessfully to serve the indictment on the defendants. 

Mr. Mueller’s attorneys said they wanted to ensure the proper process was followed. Mr. Dubelier said in a filing it was the special counsel’s “own fault” that the summons hadn’t been served and described the special counsel’s motion as “pettifoggery.” 

Earlier this month, the judge overseeing the case, Dabney Friedrich, denied the special counsel’s request to delay the arraignment, and the company pleaded not guilty at a hearing on May 9. . . .

It isn't even obvious to me that there is credible evidence of hacking the DNC and others as the DNC wouldn't even let the FBI look at the supposedly hacked servers.

From CNN: "FBI repeatedly stressed to DNC officials the necessity of obtaining direct access to servers and data, only to be rebuffed until well after the initial compromise had been mitigated.... [had] rely upon a third party for information."

The DNC claims: "the FBI never requested access to the DNC's computer servers." The FBI says that they have had to rely on third-party sources to determine if the DNC servers have been hacked, presumably that is a significantly less reliable method. Does anyone believe the DNC claim the FBI never asked to look at the servers is credible?