...When it had been established previously that the Ferengi had closed minds that she couldn't read.
Actually,all that was said in "Last Outpost" was that she could sense nothing, which "could mean" they are shielding their thoughts. But she could have been dead wrong, and the planet below could have been the reason for all the communications problems.
It's only later on that other writers (perhaps mistakenly) take the cue and write Lwaxana Troi herself as being unable to read the Ferengi.
Picard is a bit slow on the uptake here: a mysterious Constellation
class starship appears, Bok then rants about the Battle of Maxia for minutes, and it is only with absolute visual ID that Picard seems to understand he's facing his old command again. Are Constellations
really that ubiquitous in the Trek universe?