Many people think that if you're stronger and or taller, you'll always win a fight but that's not always the case. Obviously you have a good advantage if you're big and strong but that's not always enough. You can be skilled in hand to hand combat, tall and strong, but you aren't going to always win.
Size and strength aren't the only things that play a role in martial arts. You also need dexterity, agility, knowledge/Intelligence, reflexes, pain tolerance, technique, strategy, reflexes and a lot of fight in you also known as fighting spirit. I'm not promoting violence, this is just trivia. https://www.jiujitsutimes.com/david-and-goliath-why-are-smaller-competitors-able-to-defeat-their-larger-opponents/
1.) Fedor Emilianenko defeats Hong Man with a armbar submission.
In this fight, the bigger man had the advantage in height (7'2") weight(353 lbs) and strength but the thing is, he was facing Fedor Emlianenko, one of the greatest mixed martial artists in history.
Satoshi Hasegawa defeats Semmy Schilt
Semmy Schilt is 6'11" and weighs 290 lbs pounds, and he lost to a much smaller man named Satoshi Hasegawa, Semmy Schilt is a very skilled fighter and has a decent record but his size and strength advantage wasn't enough. You might recognize Semmy Schilt because he played the big guy Jason Statham's character fought in the third Transporter movie.
Ikuhisa Minowa defeats Bob Sapp
Ikuhisa Minowa is of average height(5'9") and weighs 193 pounds. He defeated a 6'5" 329 pound man with a submission. Ikuhisa Minowa is called "the giant killer" because he has defeated so many larger opponents.
Fedor Emilianenko defeats Tim Sylvia
This fight was very fast and ended with Fedor easily defeating the 6 foot 8 Tim Sylvia with a rear naked choke.
Masakatsu Funaki has defeated Semmy Schilt twice.
Masakatsu also defeated some of the best MMA fighters such as Bas Rutten, Ken and Frank Shamrock.
There are many more occasions were a smaller person beats a larger and stronger person of equal skill. In MMA there are so many rules you have to follow such as no small joint manipulation(finger locks submissions)m but in a street fight were it's no holds barred, finger locks work so well against stronger people but you need to have good dexterity to be able to perform finger locks. Finger locks such as yubiwasa techniques are mostly used to prevent a fight from happening in the first place. Keep in mind that martial arts aren't restricted to hand to hand combat, there are various martial arts involving weapons, such as pocket sized/compact weapons.