Why do so many Second Chance MC's just play Videogames?

Spoken like one who didnt study the demographic reading the novels.
Seriously though, you are asking a question that you answered yourself.
You named so many games but could hardly name a truely profitable company.
Neither Tesla or Bitcoin could be considered sound investments for anyone who knows what they are talking about.
Just like you, the  authors know more about gaming than investment, so it is easier and more believable to write about what you understand.
Good investment  opportunities would be companies like Alibaba then you have your usual suspects like Apple, Google and Microsoft.. also Amazon.
If you want to read such a novel, here you go
https://www.novelupdates.com/series/god-of-money/
 

God of Money did bitcoin and ICO and btw I learned a lot about data analysis from this series.
Extraordinary Genius reincarnated and became a VC
-the only 2 I remember that used their old memries to get rich 

Well, its either that or business. We never get the normal life ones, we have one in japanese but the mc dude gotten crazy insane. Other than those we have korean/Chinese apocalypse/fantasy/godpocalypse ones 

I think that this is for the cliché of otaku because many second mc are hikkikomorri or with no social life or there friend are just other otaku . Or this is just for them to have a cheat code because you have many of them who are reincarnate in an rpg or otome game if they don't play that this is like they are blind without any warning. 

I can only think of one story where they go back in time to play a game. In it, MC had another goal, which was to get revenge. One Man Army, I think?

Most others have a catch, or aren't set in the modern world...? 

Are you a professional gamer? Most of these time travelers are or could be. Do you think if Kobe Bryant or Lebron James went back in time they wouldn't join the NBA? That they'd just invest in stocks to get rich and that's it? No, they'd probably use the second chance to try to make themselves the unquestioned greatest player of all time. 

Great Thief
Reign of the Hunters
Pierce Heaven til it Breaks 

Novel MC's and their authors are hardly a beacon of intelligence. The main issue though is that there's not really a story of starting from the bottom and grinding to the top if you just buy FANG shares and wait 10 years to be rich. Although that's the most logical outcome in reality. 

I would hug my dad at least one more time before the cancer took him from us. That is what I would do with my second chance. 

Off the top of my head, there's Emperor of Solo Play, Rebirth of the thief who roamed the world, and Rebirth of the Legendary Guardian. I know I've read at least 1 more, but can't remember the name of it 

lol There are novels like that? Must be Qidian stuff, huh? Never read any stories with that kind of plot. Well, Ai-chan do read second chance stories, but they're all about making amends and fixing their mistakes in the past, not going back to the past to play games. 

I would like to learn a lot of language and save my money ~~