It’s a reaction to a reporter at a NASCAR event hearing the crowd yell “Fuck Joe Biden” and pretending they said “Let’s Go Brandon” - they basically just ran with it. The entire connection between the two is a reporter openly lying about what a crowd was audibly yelling. This resonates hard with the sort of people who believe the mainstream media (meaning all major news media except the largest cable news network, of course) is extremely deceitful at every turn to protect a Democrat agenda.

From another answer the user provided in this thread, it sounds like the point was saying “Fuck Joe Biden” while self-censoring themselves because they felt like the reporter who said the NASCAR fans yelling “Fuck Joe Biden” said they were saying “Let’s Go Brandon” as an act of censorship.

So pretty much the point is saying “Fuck Joe Biden” without actually saying the words, which is what we all thought they were doing, while adding some sort of ironic anti-censorship tweak to it by censoring it.

Sounds like a long way to go when they could have just said “Fuck Joe Biden.”