The Hobby and it's History
Sports trading cards can be traced back to the late 1800's, then known as trade cards. Trade cards were promotional cards inserted into packs of cigarettes that displayed advertisements for the tobacco company as well as images that appealed to their male customers (nature, war, sports, etc.) This is where you will find the most expensive baseball card of all time, the 1909 T206 Honus Wagner card, distributed by the American Tobacco Company. 
The hobby went through one of it's first dry spells in the early to mid 20th century. With many different gum companies deciding to start putting baseball cards into their packs, there wasn' really anything game changing happening. Until 1950, when the Topps Gum Company (yes, they were originally a gum company) decided to get in on things. While most baseball cards before Topps simply would put the players picture and maybe biography on the card, Topps were the first to incorporate the synonymous playing record and statistics on the back of the card.
Topps dominated the market for decades, buying out their competitors (Bowman) and branching out making sets of other sports and even some non sports genres (Star Wars). This dominance lasted throughout the 21st century and while one competitor, Upper Deck, could never get near Topps, Panini has been able to catch up and surpass them in recent years.
In 2009, Panini go the exclusive rights to produce NBA basketball cards, and a few years later they got the NFL's rights as well. Due to the popularity of these two compared to where baseball is today, along with many innovative sets and designs, Panini has become the now undisputed king of sports cards. Benefitting the most from the recent boom in card sales. But that might not last long. In 2021 it was announced that Topps were losing their exclusive MLB rights to Fanatics, a sports clothing and memorbilia store. A few days after this, it was learned that Fanatics also acquired the NBA and NFL rights, giving them a monopoly on the sports card market. This has caused some obvious concern from collectors. "Will the quality decrease due to them having no competition?" "These rights acquisitons are years away and coming at different times, will Panini try and mass produce cards to saturate the market?" We will just have to see, but the with the recent highs, we should expect some lows in the future.