The reason why Football and Baseball are/were perceived as more popular is simple:
Eight college football stadiums with 100,000+ seating capacity.
Dallas itself has a stadium that seats 92,000 The Cotton Bowl, that doesn't even have a team or college associated with it. It's just used for rivalry games.
Dodger's stadium seats 56,000. The fewest seats in a baseball stadium is Tropicana Field in Tampa Bay with 31,000. Fenway only holds 37,000.
The largest basketball arena in the world is in the Phillipines and holds 55,000.
Largest in America is the Syracuse Carrier Dome with 36,000
Largest in the NBA is the Chicago Bull's United Center and it only seats 20,917.
The smallest baseball stadium is as big as the largest (American) basketball arena.
And the largest football stadiums hold 5 times as many seats as the largest NBA arena.
94 x 50 feet. 4700 sq feet is the area of a basketball court
160 x 360 feet. 57,600 feet is the area of a football field.
A soccer field is similar, 54,000 sq.ft - 86,400 sq.ft.
The baseball diamond itself is 8,100 (a square with 90 feet sides) and that's not including the outfield which can vary.
The size of a sport's audience is dependent upon how many fans can watch a game at any given time.
How many fans can watch a sport is determined by the size of the field of play the sport uses.
Football, baseball, soccer use noticeably larger fields of play than basketball, and so have a larger viewing audience.