There was an infamous supreme court case[0] in 2010 which has set off a steady increase in campaign. Before that influencing campaigns with money was much more regulated.
Since then it seems to me (I am not an expert in this) that there's been basically a race to the bottom in politics which Donald Trump correctly identified, and has had basically a "pay me and I'll do you political favors nakedly and nobody can do anything about it" approach, which appears to be a winning strategy, unfortunately for the system as a whole.
edit: I seem to have also missed a ruling this past march which had an impact:
> America PAC’s work was aided by a March ruling from the Federal Election Commission that paved the way for super PACs to coordinate their canvassing efforts with campaigns, allowing the Trump campaign to rely on the near-unlimited money of the nation’s most high-profile billionaire to boost turnout in deep-red parts of the country.
Since then it seems to me (I am not an expert in this) that there's been basically a race to the bottom in politics which Donald Trump correctly identified, and has had basically a "pay me and I'll do you political favors nakedly and nobody can do anything about it" approach, which appears to be a winning strategy, unfortunately for the system as a whole.
edit: I seem to have also missed a ruling this past march which had an impact:
> America PAC’s work was aided by a March ruling from the Federal Election Commission that paved the way for super PACs to coordinate their canvassing efforts with campaigns, allowing the Trump campaign to rely on the near-unlimited money of the nation’s most high-profile billionaire to boost turnout in deep-red parts of the country.
source: https://apnews.com/article/elon-musk-donald-trump-election-2...
[0] https://en.wikipedia.org/wiki/Citizens_United_v._FEC