Marcus was not a weakling. Since he had been trusted by Joseph to take care of things in his absence, then not only did Marcus have to have a minimum cultivation, he needed to have proved himself over the years. He was a mid level Nascent realm cultivator, with excellent administrative experience as well as battle experience in skirmishes against neighboring nobles.
All in all, he could be considered to have vast experience in various fields. Yet at the moment he found himself completely at a loss. He did not even consider how Lex was able to discover his intentions, for that no longer mattered.
What truly befuddled him was how Lex was able to trap him after he had already left. After all, the opaque barrier surrounding him had not appeared until he tried to enter the control room. Moreover, the fact that Lex's voice spoke to him after the barrier appeared also meant that this was no accident.