The reason for BB being hit is one and only one: Contestants. This year BB brought gamers. Everybody remaining in this game played their game to full potential. I understand, we support our favorites, but BB is more than just fandoms. Let me try to look at bigger picture.
Everybody came with some game plan. Some had only one plan, some had plan A, then plan B. But there are two things every one plans. Keeping Friend and Foe all the time.
Shukla- Rashmi played on his mind 24/7. He always considered Rashmi as main rival. His game has revolved more or less around Rashmi. Whoever is Rashmi’s friend is Shukla’s enemy. First Paras and Mahira, then Asim and Vishal. Sana and Arti been cordial to Rashmi, so they were not considered loyal even if they stuck with Shukla from beginning.
Paras- Paras has the most cunning strategy. Paras has very keen eyes on judging person. He had fought, but he always knew those fights are not real. That is why he fights and laughs both together. Actually, he did not fight with anybody in 4 months. He clearly knows where is the line. He knew which friendship will benefit him. He switched to Shukla side on first opportunity. And stuck with him like anything. Remember, they know each other from outside.
Sana- Sana was kind of outsider, she was not close to anybody before BB. It was difficult for her to survive. She knew the strength of her friendship with Shukla. She knew, this friendship is not based on trust. She never trusted Shukla, so, she wanted to keep friendship with other in the name of search for entertainment. She reached so far.
Mahira-Mahira followed Paras. She stuck with Paras, but she is not as close to Shukla as Paras from outside of house. She tried hard to make enemy angle with Rashmi, not that strong because Rashmi is different person.
Rashmi- Rashmi game plan has always been at same plot, that is around Shukla. She tried to mix hate, foe, joking angle in the show. But Rashmi game was not going anywhere because of her mild personality. BB brought Arhaan, then BB tried to get sympathy for her. BB had to work hard on her. One thing about Rashmi is that she values friendship, she never backstabbed. She cane out as nice person.
Arti- She was in depression, just to boost her confidence, BB kept her in house away from her real world. Actually, she played her role well. Her stepping into everybody talk was not bad.
Asim-Asim journey is the most unexpected. Whatever Asim is right now. 50% is because of him and 50% because of circumstances. He was on target of Paras from day 1. Because Asim was new to TV industry, nobody knew him except Salman(my guess). First few weeks were very tough, but because of his looks and Salman he survived. He got enough time to analyze whole game, HMs strength and weakness. His individual game plan was same as Paras, enemy-friend. Same as Paras, Asim jumped the boat immediately when fight with Shukla happened. There is no better way to go against the main guy. He used his strength, like guts, dialogue delivery, monologue, nice side of accepting his mistakes. And he knows how to get reaction from other and then turn that to his favor. He used his strength and other weakness very smartly. He is good learner, he learned the game while playing the game. He learned one thing that there is no friend in this house, so play for yourself.