Headscratchers / Star Trek: The Next Generation S1 E24 "Conspiracy"

• Why did the aliens engage in such carefully subtle operations throughout Starfleet that the details of the conspiracy were unnoticed until Data explicitly started looking for them, only then to unmask themselves well into Evil Laugh territory when the D arrived at Earth?
  • Data's search for them started after Captain Keel got Picard involved in matters, so building on his own investigation (which had led to his own death and the destruction of the Horatio). Considering that by later appearing among the infested officers, Captain Tryla Scott was presumably infested either before Keel's meeting or very shortly after, and with Picard outright saying that the Enterprise has been far from Earth in the time since "Coming of Age," when Admiral Quinn first alluded to the conspiracy, the Enterprise was free of infection to that point - but, when the Enterprise, known to have been at Keel's meeting, shows up on Earth's doorstep, the parasites reasonably assumed that Picard had already figured them out, and they just indulge the cliche because Picard is already marked for infestation, with them having summoned Picard and Riker down (and Quinn going up to the Enterprise with another parasite). Having already gotten most if not all of the staff at Headquarters, they clearly assumed themselves to have the advantage.
• Maybe blooper territory, but having just discovered the blue gill, Riker startles Beverly, then they decide and implement the ruse of Riker being infected by the alien and beaming down to help Picard. This could have been minutes at best, but seems more like seconds.
• Would Picard and Riker have blasted Remmick if they hadn't already despised him?
  • Considering they've already fired on Admirals, meaning their superior officers, probably. They don't immediately blast Remmick - Riker even tries to warn him about the approaching parasite before he reveals that he's among their numbers. Then Remmick willingly takes in the parasite, his neck begins bulging, and he gives the Blatant Lie of "we seek peaceful coexistence," which is coming after the parasites infiltrated Starfleet Command and were responsible for several deaths (while brought up by the infected Captain Tryla Scott, both Keel and Riix don't dispute them), and the destruction of Keel's ship, the USS Horatio, which was identified as an Ambassador class ship, the same class as the Enterprise-C, holding somewhere in the range of at least 700 crew. "Peaceful coexistence" did not seem to be an option, so when the creature inhabiting Remmick reveals itself, Picard and Riker respond to its intentions in kind.