Lawsuits of course cost money, often lots of it. But they are also cumbersome, time-consuming, stressful affairs that wear down both the people involved and the media that reports on it through sheer attrition. Even if someone is willing to take on Trump, it's difficult to keep the public engaged with years of piecemeal updates while so many new stories unfold. How many of you are still following the saga of Trump's tax returns? He said he would release them, then came up with inane excuses not to, then got belligerent, and finally he's thrown every possible legal obstacle at the proceedings, to the point where he may not even still be president by the time it's resolved.
Trump's court record is mixed, and his administration's record specifically is awful. But winning a lawsuit is tangential to the aims of launching one, which is to drag issues out until they're forgotten, or at least distanced from the Trump who lives in the present. As a bonus, lawsuits let him bluster about how great he is, like when he presented a suit against the city of Minneapolis over the cost of security for a Trump rally as the mean old Democratic mayor trying to suppress his followers' free speech. Then, if he's proven wrong, he never has to mention it again.
So in 2019, Trump sued Deutsche Bank, Capital One, the chairman of the House Oversight and Reform Committee, and many, many more in an attempt to kill inquiries into his finances. The suit against the committee chairman was described as both "unprecedented" and "not likely to prevail." But analysts also pointed out that all these suits dropped the issue into a complicated legal morass from which it may not emerge until after 2020, at which point it would barely even matter.
Trump's lawsuits have included hundreds of cases in which his employees and contractors were never paid. He could have just paid his damn bills -- some of the claims were for only a few hundred dollars -- but he instead insisted on dragging the claimants through the courts until they gave up, went bankrupt, or finally settled on the condition that they could never discuss their cases. When these stories came out in 2016, they did absolutely nothing to his presidential campaign. Why do stories like these not break Trump like they have so many other candidates? Well ...