As I understand it, late July is when the political parties start getting results from top-top-level professional pollsters, the ones who get paid large sums of money to produce very accurate polls (which are generally not released to the public).
July / August is when, if necessary, big campaign changes are made.
As an example, It was August 2016 when Bannon / Conway replaced Manafort as Trump's campaign manager.
My best guess, in addition to my previous post about the "get people talking about Trump's latest outrageous statement instead of say, 150,000 dead Americans from Covid or the economy contracting at an unimaginable rate or not bothering to even mention to Putin about the Russian bounties paid to the Taliban for killing American soldiers"....
...is that team Trump saw the "real" and far more reliable poll numbers, saw that if things remain as they are now, Trump will lose by 200 or more electoral votes, not to mention the popular vote by 10-12%. I.e., likely the most humiliating loss by a candidate since 1984, and the most humiliating loss by an incumbent since Jimmy Carter in 1980.
So, team Trump's "strategy", for lack of a better term, is to try to cast doubt on the legitimacy of the election, mainly so that when they lose, they can spin it into "See? We told you it was fixed" and then start up their own "b*tch about the damn liberals" media network and make gobs of money....
(Which, I think, was their real strategy in 2016. I don't think anyone on their team seriously expected to win)