Since 1920, 12 players have won the triple crown (it has been won 12 times but Hornsby and Ted Williams each did it twice) and three other players led their league in HRs and AVG but not RBIs. So 80% of the time a player leads in the first two stats they win the triple crown. Click here to see the Baseball Reference list of triple crown winners.
Ted Williams, 1941 is the other player besides Mize and Ruth to fit this category.
Here are the leaders in the AL in 1924:
How could Goslin get more RBIs than Ruth? Goslin hit 12 HRs and batted .344. Ruth beat him in TBs 391-299 and in extra-base hits 92-59. Ruth only beat him 200-199 in total hits, however.
Ruth batted 3rd in all but one of his 681 PAs. Goslin had 624 of his 674 PAs batting 4th and the rest 3rd.
Here are the stats for slots 1-3 on the Senators (with Goslin removed from the stats for slot 3)
Here are the stats for slots 1-2 on the Yankees
The three guys in front of Goslin had about a .359 combined OBP. Those guys averaged getting on base about 248 times each.
The two guys in front of Ruth are about .345. Those guys averaged getting on base about 240 times each.
It looks like the Senators might also have had faster runners with their higher triple and SB totals.
But it seems like this would not be enough to overcome Ruth's huge lead in HR's, TBs and extra-base hits. Maybe Ruth got walked alot with runners in scoring position. He had 142 BBs and Goslin had 68. That gave Goslin an extra 74 times to swing the bat and they were both pretty close in total PAs.
Retrosheet does not have the splits for batting with runners on and with runners in scoring position. Maybe Goslin did unusually well that year. Until we have those splits, we can't be sure what allowed him to have more RBIs than Ruth.