The Gracies modified old-school Judo to make it able to defeat bigger men. No Japanese martial art was made specifically for fighting bigger men. On the contrary, if you read accounts from the original Judo guys in the 1800s (yeah the founder was a normal sized guy at 5', but his 'best students' were not), it was encouraged to scout for big guys and small guys were frowned upon as poor prospects. By "big", I'm talking like 5'6" lol. But in that time period in Japan, that'd be like being 6'4" today.
Not true at all. Robert Drysdale in his new book "Opening Closed Guard" says how the Gracies didn't actually make any changes at all to Judo but that BJJ started to surpass traditional Judo on the ground in the 90s as a result of BJJ competitions elevating the art.
Who do you think will win a 5' BJJ 30 yr old black belt or a 5'6 BJJ 30 yr old blackbelt? The advantages of size and strength is found in all martial arts.