The police can't go breaking down doors or even picking locks and entering every single locked resident in Big Bear without some sort of justification as to why they believe their suspect may be hiding in that structure. I can only imagine the outrage and the lawsuits if they had indeed done what you and some others on here expected them to do. With that being stated, if they had suspected he was in there they would have entered. Come to find out NO ONE in that area, including neighbors, other house cleaners, media right next to the building, etc. knew he was in that particular structure either.
He could have easily have carried all of his weapons, ammo, etc. himself. Perhaps he had some gun cases? We don't know because that information hasn't been released yet (as far as I have seen.) We are talking about approximately 2am in the morning in an area of town that is very quiet once the lifts shut down. I have been in that area before at 5am, 6am, 7am and never see a sole. Plus I suspect he was moving in a stealth manner instead of barreling down the middle of the street
Dormer knew that LE would have to get search warrants to search any empty cabins, houses or condos at BB, unless they showed evidence of forced entry. His choice of BB gave him many good opportunities to find a place to hide where it might not be practical for LE to search for him. He was smart and lucky enough to find a condo that was unlocked, where he knew they probably wouldn't enter for lack of a SW.
Before his truck was disabled, it appeared he carried enough equipment with him (items left behind included a cot and bedding, etc.) that he planned to hide out in one of the many vacant summer camps located south of BB. When his truck became disabled, he probably carried what he could (including large arms and ammo, since reports found his tracks with indications he was dragging something heavy with him) to the closest possible "safe" location - the nearby condo. Since he carried a lot of gear with him, it probably included MRE's - enough food to take care of his needs for at least a few days, if not more. There was evidence of him visiting other vacant cabins, probably for food and other items. I doubt he went into town to acquire provisions.
He lucked out in finding a condo where he had access to water, toilet, bathing and cooking facilities and probably a television and radio and an unobstructed view of the command center. He was probably able to view a lot of details about the search.
He made a break when he was discovered and, when he couldn't get out on a major highway, holed up in the best place he could find. At this point, he knew he probably wasn't going to get out alive and took out as many LE as possible before committing suicide.
He saw himself as a martyr. He sent his messages, wrote his manifesto and made his case to the public, grandiose as it was. He used his skills and the element of surprise, but he also caught some lucky breaks. He had to know how it would all end. After everything that had happened so far, it ended the only way it could have. He would not have surrendered. He knew that, because of his choices and decision not to surrender, he was a "dead man walking" and LE had few options left.
As someone who spent quite a few days monitoring the scanner and following his moves in BB, right up to the end, this is my best assessment of the situation. I'll say monitoring the scanner 12 to 14 hours a day the last few days was an emotionally exhausting task and I was somewhat traumatized by all of it. In the end, given his decisions, there was no way it could have ended differently. He went on his own terms.