Why did I play it? This is in a tournament. I'm playing the site #5 who is 200 BKR points above me. We're level in our tournament section on points though he's played one more game than me. I can take the immediate draw or take the risk of winning but possibly losing. Will a draw satisfy me in those circumstances? You bet. Have our BKRs changed as a result? No.
Could black have stopped this? Possibly. I hope so. Otherwise the Tablut rules are definitely flawed. If black did not want a drawn game, and it was possible to stop it, then he would have (or should have) taken this into account at the outset.