Now, as to be expected, the chemistry is bullshit.
The mass media doesn't know jack shit about what it's discussing. I think it's likely the timing of these arrests was not chosen for investigative purposes, but entirely political ones. If you wanted to further an investigation, you'd have let these guys run longer. Let them complete their dry runs, observe them well, rig the computers to flag some of them as selectees and cavity-search them and their carry-on contents. (Learn what type and brands of personal effects they carry.) Let them buy their chemicals. Then bust them. Build a solid case, so no jury would question how serious these guys were. But if you wanted to stir up fear for a repeat performance of the 2004 election cycle, then you arrest them now, between the last primaries and the general elections.