After the sudden appearance of the Fallen Clan's forces, the team in charge of breaking into the Darkshell Citadel had gone from seven in total to five.
(Technically it was ten to seven, but for the purposes of keeping track, we won't be counting the kaijin that are currently inside of human hosts, i.e., Razorstella and Screamira...yet.)
While this wasn't a massive reduction in combat power, this was a massive reduction in the ability to gather active intelligence and coordination.
Zhen Liu's brain was directly connected to the [Library of Nowhere], and while the Kaijin could technically relay this information as well, their somewhat erratic behavior made it a bit harder for them to come up with plans that didn't boil down to "break everything then run".