Zero days may get the headlines, but attackers are finding a lot of value in leveraging old vulnerabilities. CISA, FBI and NSA have issued several advisories over the last month highlighting an overarching theme of advanced persistent threat groups targeting unpatched vulnerabilities lately.
I observed something similar that began earlier this year. I wrote about it on the Tenable blog. They impersonate many of the people following Trump and engaging with his tweets, irrespective of party affiliation.
It's true that all of the platforms you listed have dealt with scams over the years. It's part of the maturation process of any social network. In the case of TikTok, it officially just celebrated its 2nd year as a platform, and I just began to observe a slew of ads on the platform pushing scams unabated. Scammers follow the trends and where the users are, so an extremely popular app like TikTok became a platform ripe for the picking.