It wasn't a lame fight, he learned how to grapple and that's not Tora's strength, it's obvious he's a stand up brawler, this shit happens in real life all the time, if you become too complacent with your skills you lose the hunger to grow, it was obvious Tora lost that hunger because he was "too strong". Now he's not, he knows his weakness and the MC learns that even his master has limits.