If Republican leaders came out and said that Joe Biden is the President elect then there'd be much less traction for this kind of thing. Instead we have them supporting President Trump, echoing his "every legal vote", supporting his lawsuits and making reference to a second Trump term.
People would be more sanguine about an orderly transfer of power if the GOP seemed at all interested in it. Instead they seem to be doing everything they can to obstruct and frustrate. At the moment it's "just" not allowing the release of funds for the transition and not allowing Joe Biden access to security briefings - in part because the US public aren't making a big deal out of it.
If they (they in this case being both the national Republican leadership and the state leaders in those states) think that the blowback will be worth it, then why not take these entirely legal steps ?
edited to add......
We've heard it so many times in recent years, "They won't/can't do that". Whether it's refusing even to consider a SCOTUS nominee and then forcing through another in similar circumstances, the myriad cases of President Trump behaving in ways which would have bene previously unthinkable or embracing groups who would otherwise be anathema to the party, the GOP is breaking new ground all the time.