Why did Bhishma last longer as a commander in the Mahabharata compared to Drona and Karna, despite all being skilled warriors?

Why did Bhishma last longer as a commander in the Mahabharata compared to Drona and Karna, despite all being skilled warriors? Lasting long doesn't mean he was most efficient general. In fact, he was 2nd most pathetic commander after Shalya. Under his command, pandavas did not lose much significant warriors, nor major destruction for pandava army whereas Kuru army lost 2 akshouhinis. As for why it took longer, Bhishma was most protected warrior in the entire war, Duryodhana always strived to protect Bhishma from others. This can be seen on plenty of instances., 10th day at its best. For each successive general, this reduced greatly. Moreover each general among Bhishma, Drona and Karna were killed when Krishna decided to put them down.. Bhishma's commandership was hardly problematic for pandavas for first 8 days, in fact it was quite the opposite. Things were not going so greatly for Kurus. Provoked by Duryodhana’s harsh words on 8th night Bhishma tried to cause maximum damage to the army on 9th day. At this point Krishna decided to put him down and used Shikhandi as only Shikhandi' was capable as per Shiva's boon. For Drona's case, he was best in case of building and holding battle arrays. Even most complex arrays. The most powerful Vyuha was formed on 14th day (combination of 3 arrays - Chakra-shakata, suchimukh and Padmavyuha). The Chakrashakata vyuha was the outermost array guarded by Drona and it was only penetrated by 3 warriors, Arjuna through avoiding Drona, Satyaki and Bhima by vanquishing Drona after multiple failed attempts. The most impressive fact is none else apart from these 3 succeeded in entering the array till night. Dhristadyumna scattered this array multiple times but Drona held it together till evening. Not only that he killed multiple prominent warriors on that' day. Even more impressive is the fact that Shiva weakened Kuru army on 14th day as a consequence of his boon to Arjuna. Drona’s form on 15th day was so fierce, none could stop him. Krishna feared he would devour the army on that day itself and realised the need to put him down immediately by hook or crook hence used treachery, ie the famous Ashwatthama’s fake death Incident. This event later proved fatal for Pandavas. Ashwathama in rage unleashed two most powerful weapons in his arsenal extinguishing more than 1 Akshouhini. Drona's tenure was utter bloodshed in both sides severely weakening both armies. Kurus lost 4 full akshouhinis and Pandava army lost 3 full akshouhinis. And it would've resulted in more destruction for pandavas had they not cheated. Karna, as a general, proved highly effective, with both sides suffering almost equal losses, each losing about two akshouhinis. During earlier tenures, the Pandavas inflicted greater damage on the Kaurava army. Unlike Bhishma and Drona, who relied more on strategies, Karna’s command resembled a one-man show. In just two days, he decimated nearly 1.5 akshauhinis and became nearly unstoppable on the 17th day, armed with a more powerful divine bow. He could've won the war by capturing Yudhistira, but instead spared him out of benevelonce or promise to Kunti. Even Arjuna struggled greatly against him, resorting to multiple celestial weapons and even invoking the so called Mahapasupata against the adversary. Earlier, Krishna strategically pulled him out of the battle to save him from Karna when the latter unleashed the Bhargavastra. Eventually fate became the villain in Karna’s case,. When his chariot wheel sank, he lost morale and clearly showed weakness afterwards, leading to his downfall. Bhishma's achievements in 10 days combined too does not equate to Karna’s one on 17th day alone.