Judges 16:28 And Samson called unto the LORD, and said, O Lord God, remember me, I pray thee, and strengthen me, I pray thee, only this once, O God, that I may be at once avenged of the Philistines for my two eyes.
16:29 And Samson took hold of the two middle pillars upon which the house stood, and on which it was borne up, of the one with his right hand, and of the other with his left.
16:30 And Samson said, Let me die with the Philistines. And he bowed himself with all his might; and the house fell upon the lords, and upon all the people that were therein. So the dead which he slew at his death were more than they which he slew in his life.
Samson may be a strong man, but to topple two pillars, he must have some help from God. And maybe Samson also asked God to grant him very long arms to be able to push against two supporting pillars with enough leverage..
Certainly Samson had some help from God because he asked for it and despite his moral defects Samson was used by God to deliver the Israelites.
The theory about the 'miracle' of arm lengthening is indeed intriguing. It would be interesting to see the archaeological, textual, or other evidence on which it is based.
Certainly also, whatever the situation with the pillars, sufficient strength was granted to do the job. Perhaps he lent on them alternately and got the building to sway and then topple. Four thousand people on the roof may also have put stresses on the structure already to which the activity of Samson was the last straw. Whatever happened, it was not at all outside the realms of possibility.
If the Philistines sent for him to be mocked and whipped, then he would have been tied up to the pillars. I have seen the different ways they made pillars back then and most were segments so really it wasn't one sold structure but many blocks carved (like stacking Lego). Still if God grants you strength he an't gonna do it by half