If you're in the minority - and if you realistically expect you're going to continue to be in the minority - then you might well want to erect barriers to voting, or vote-counting, that differentially impact those voters who are less likely to be your supporters.
This isn't democratic, of course - it's simply manipulating the system to gain or retain power, notwithstanding your minority status.
It's only a "terrible precedent for the future," from a partisan viewpoint, if you expect to ascend to the majority at some point in the foreseeable future.
Trump's Republican party has become the party of a subset of white Americans - the very successful and wealthy, on one end, and those who hate/fear anybody who doesn't share their race/religion/language/culture on the other end. But the economic elite (the "1%") will always be a small group - by definition; the rural, white conservative Protestant population is shrinking, and will continue to shrink. I grew up in rural America - younger people abandon their rural homes in droves, because there's no future there for those who are ambitious or talented, and with the decline of unionized manufacturing in the USA, there's less future for those who may be less ambitious or talented, either.
The USA is becoming less white, less religious, less rural. Trumpism has driven most "conservatives" who aren't racist, religious, and under-educated (or alternatively, very wealthy and able to buy influence in the party) away - either out of the party altogether, or effectively neutered politically. The Republican base is shrinking, and will continue to shrink. But the party wants to keep power. Manipulating elections by creating impediments to voting by all the non-white, non-Christian voters is about all they've got left.