Because......
They are winning all their home games.
They have fan groups like the Spirit of Shankly who organise flag displays, etc.
FSG are compelled by those groups to work with them.
Cast your mind back to the proposed season ticket price rises FSG wanted to bring in. Liverpool fans protested and up to 10,000 fans walked out during the match. The price rise never happened. That would never happen at City. Liverpool are the closest thing to an Ultra minded fanbase in England.
They also have a 20,000+ seater KOP that ‘now sings’ and get’s the rest of the ground going. And because the vast majority of their fans buy match day tickets, and there season ticket holders are limited, they have a rotating fanbase, whereas we have a static fanbase, as we have over 40,000 season ticket holders.
Only a few seasons ago LIverpool where s***. They were a good 20+ points behind us when we won the PL. Losing and drawing their home games. The atmosphere at Anfield was gash. You could hear a pin drop bar YNWA at the start of the match, and the same few Liverpool chants sang briefly after each goal. Don’t be fooled by this mystic notion about their support. Yes, their support is good now, why wouldn’t it be? CL winners, top of the PL, unbeaten home and away, etc. Their fans are loving it and lapping it up atm.
As for United’s away support. It is the best. Because most of their away support tends to consist of young Men in their 20’s and 30’s, who began following United through the Fergie winning years, and who are very vocal. Compare that to our away support. Most of our away support is in their 40’s, 50’s and 60’s. Including me. The same fans who have amassed away loyalty points over the years.