Originally posted by: proteeti
Bheem's poisoning: this one's quite simple. Kunti didn't want to risk being sent away by drawing attention to the living-there prince's shortcomings. She needed to be in the heat of the things.
Lakshagriha: till now they did not have Krishna's direct support. Without that, they were cunning-wise no match for Shakuni. In order to make up for Shakuni's quick shrewdness, they needed time. By hiding after the Lakshagriha incident they (actually Vidur) made Shakuni believe that 5bros are dead, and by believing this, Shakuni left Dury and Dhrity to their devices for a while and did not harm Hastinapur any further.
Also, by roaming in disguise through most of the Kuru kingdom, they found out what the people exactly thought of 5Ps and Dury&co, and by potentially manipulating with people's view of Dury&co., they actually were able to make more damages.
Unless they had met Krishna at Drau's swayanvar, I doubt they would have resurfaced even after that.
If they would have returned to HP immediately, Shakuni would have started on another plan, and this time would be wayy more careful, and there was no saying if 5Ps would survive the next plan. This way, they could cool off and also, give Dury&co. the false sense of security taaki when they did come back, they would be taken by a shock and would be able to do less damage.