The history of sushi is long and expansive.

It started literally centuries ago, when people first wrapped fish in fermented treated rice throughout parts of coastal and riverside Eastern Asia as a method of convenient preservation. I don't actually know a great deal about the intricacies of it during this time period so I'll leave that for someone else!

It should be noted here that the word 寿司 sushi refers to the rice, and not the fish. Interestingly the kanji here are used simply for their phonetic sounds rather than their semantic value (the individual characters here don't actually relate to sushi, unless you make a wide stretch and argue that 寿 which can mean 'long life/longevity' is related to the original intention of sushi to preserve fish). Anyways.

Moving ahead, by the Edo Period (16th century to the mid 19th century), sushi was a well established cuisine in Japan, with dedicated restaurants and was prepared in a distinct style for gourmet appetites rather than for practical preservation value.

In the capital, there were many sushi establishments as well as street vendors that sold sushi. By this time, the fermentation process was being limited in favor of more delicate, subtle flavor profiles. Fish was also no longer simply wrapped in fermented rice to keep it preserved but was dipped in soy sauce, salted, smoked, cut or otherwise prepared in various forms and ways.

It should be noted here that wasabi root was originally one of the ways to help keep fish fresh while adding a powerful flavor profile.

Sushi, at least for the elite in Edo, was becoming more sophisticated, but the sushi that most people ate still wasn't considered haute cuisine, nor was it similar to what we eat today. This is also when raw fish was starting to be used in sushi as it was beginning to become a food that was ate soon after preparation as opposed to being preserved for eating much later. This was obviously limited in scope because of the lack of good ways to preserve raw fish for a while yet.

It should also be noted that hand-shaped sushi, as opposed to sushi shaped with a box, was an Edo style. So all of you who enjoy your hand rolls, thank Edo! (As a side note, boxed sushi was an Osaka thing)

Fast forward to Meiji Japan (late 19th century to early 20th century)

Japan has begun enormous amounts of trade with the global community. Interest in Japan and all things Japanese explodes as one of the famous isolationist hermit kingdoms of the Far East opens up its doors.

Japanophiles from all around the world, almost all of them rich and with time to spare, journey to Japan, explore Japanese tastes, fashions, culture, and paint or write about Japan.

The period of intense Japnophilia is actually readily apparent in a wide variety of media and literature, encompassing household names like Herman Melville, John La Farge, Henry Adams, and everyone's favorite, Theodore Roosevelt. But I digress.

During this huge wave of Western interest in Japan, especially as Japan looked to modernize and cultivate recognition from Western imperial powers , many people are exposed to Japanese things for the first time. This includes, obviously, Japanese foods.

Sushi was absolutely a novel foodstuff and a curiosity for most Japanophiles. And of course, Japanophiles took these experiences home with them, whether by correspondence or stories told to friends and strangers alike.

Japanese communities that lived overseas also brought sushi with them of course. By the turn of the 20th century, many of those interested in all things Japanese had heard of or seen sushi. Some had even dared to eat raw fish!

It's important to note that this wide interest and acceptance of Japanese cuisine had a huge part to do with how Western societies saw Japan, Japanese people, and Japanese culture.

To put it bluntly, Japanese were often considered to be as close to being a 'white' person as any non-white could be. At the turn of the 20th century, Japan was doing tremendously well in it's war with Russia and much of the international community, especially the United States, was cheering for Japan! Yes, not Russia!

This kind of fascination and interest in Japanese cuisine did not, for example, extend to much of Chinese cuisine, which was still considered a cheap, 'ethnic' sort of food. There certainly weren't many societies of high class white folk who were busy trying to outdo one another in seeing who could be more Chinese. But there were many societies dedicated to all things Japanese.

This kind of fervor for Japanophilia would eventually fade, as most fads do, but as Japan was rapidly changing, it actually spurred some of the most staunch Japanophiles to search out even more Japanese things, in search of a quickly disappearing Japan. Unfortunately for sushi in America, by 1907 and anti-foreigner sentiments, particularly anti-Asian immigrant sentiments which peaked with the Gentlemen's Agreement, wide adoration for Japanese cuisine quickly vanished. But that is a story for another time.

Fast forward to the 1960s~1970s.

Japan was rapidly recovering from its post-World War II years and business was booming. Japanese food was fairly common within Japanese neighborhoods in places like Los Angeles, New York, etc.

But the first sushi restaurant in America appears to be the Kawafuku sushi bar that opened in Los Angeles sometime between 1964 and 1966 by Kanai Noritoshi with the help of Harry Wolff. This sushi bar served traditional edomae style sushi (that Edo sushi I talked about earlier!) and quickly became a huge hit.

The owner had hit jackpot and returned to Japan. Other sushi chefs saw opportunity and gathered from all over Japan to go to the West Coast of the US as well as NYC, opening up sushi bars left and right.

10 years later, sushi had steadily garnered recognition as being sophisticated enough and requiring enough talent to be considered haute cuisine. For example, look at this 1981 article about sushi being served at the elite NYC Harvard Club

By this time, there were already a ton of American derivations and takes on sushi (like the mighty California roll), but the high minded, exclusive folk of American society wanted nothing but the best, authentic Japanese sushi money could buy. And they were willing to pay top dollar for it.

And much like any other type of high class cuisine, it received more attention and growth because of high end demand. People with the money to propel growth in an industry wanted high quality sushi, and they got it. Sushi itself had evolved through several iterations between the early 1900s and the 1980s.

It also helped that Japan's economy and Japanese businessmen seemed to be taking the world by storm. The kind of news that people write about China's economic growth and the general zeitgeist that China is a major economic rival to the world's global powers is exactly how people used to feel about Japan.

This sense of rivalry or recognition of Japan as a force to be reckoned with also compelled a lot of interested observers to look at Japan and Japanese things to understand why they were what they were. This meant looking at Japanese businessmen, and of course, a lot of this meant looking at where and what Japanese salarymen ate and drank.

They drank tons of alcohol and they ate lots of ramen, yakiniku, and sushi.

By the 1990s, Japan saw its economy take a turn for the worse, but Japanese cultural exports were never more popular.

Anime, manga, music, fashion, design, art, literature, etc. Hello Kitty, Sailor Moon, Godzilla, ninjas, samurai, geisha

The world's Japanophilia from the early 1900s had been revived with a vengeance and Japanese pop culture took the world by storm.

And Japanese cuisine was obviously a part of this wave. Sushi only got more and more popular as time went on. We can't go much farther into modern times because of the rules, but sushi still retains much of what it was 400 years ago and more, while being very different.

It is at once a very humble, street or home food that is elegant in its simple form, but also rises to great heights of sophistication, complexity, and art on the plates of high class restaurants anywhere. It's multi-faceted nature and flexibility for both adaption (local non-Japanese variations of sushi) and refinement (both traditionally authentic as well as progressive, modern sushi) are no doubt a large reason for its popularity.

And at the end of the day, sushi just tastes good!

Hope this was helpful. Cheers!

maybe someone on r/askculinary can answer this question.