First panel S3:E13 “Venom Of The Red Lotus” vs. other panels S4:E07 “Reunion”

Mako and Asami love Korra so much. They are absolutely devoted to her.

Asami's life before Korra was the life of a prissy and rich girl who had whatever she wanted. She thought she was happy till she lost everything. Fortunately, Korra appeared in her life giving her the opportunity to have a purpose greater than living to enjoy the material things.

Mako's life before Korra was the life of a lonely boy who thought his mission was just to survive for himself and his brother. Then Korra appeared in his life and he started to confront greater problems living adventures with her. He learned that selfish survival wasn’t really just the mission of a human being and that you are never alone if you can help others.

Korra was raised with the love of Tonraq and Senna so she became through the years a girl full of love. Never really needed money so she never developed a greedy or interested personality. With all that, we can’t say everything was perfect for her through the years growing up in the south. With everyone serving her from the first day of her life so devotely she could have developed a miserable personality but she chose well.

Even when Korra will be learning forever how to be a better Avatar she's completely aligned with the meaning of "what it needs to be the Avatar'' from the beginning of her life. Which is to actively help people with generosity, serve the world with honesty and inspire others with your vision and your example as a human being.

Mako and Asami -each one in a social class- were living their lives just focused on their own lives. Which is fine. It isn't judgeable at all. But with Korra they learned to live for others as well because living by her side they amplified their vision of the world.

Korra gave Mako and Asami a greater purpose and meaning to their lives. That's why Korra is a constant source of inspiration for both of them.

-

Additional notes: I think both of them, seeing the way they love Korra, they were potentially love interests for her.

The problem was that Mako had a lot of issues because of the absence of love when he was a child and he ended up being an immature boyfriend. Also, Mako and Korra were too young and immature when they started their relationship. Plus, I believe Korra wasn't completely in love with him. She liked him, yes. But that wasn't enough to establish a complete relationship. So that's how Asami ended up being a better partner for Korra. Because the two girls built a solid friendship before they started being love interests. Also, they both have grown up by the time they start the relationship.