Distant Spell only interacts with the "Range:" entry of the spell description.
Distant Spell states:
When you cast a spell that has a range of 5 feet or greater, you can spend 1 sorcery point to double the range of the spell.
Notably, hold person states in its description:
Range: 60 feet
Using Distant Spell with hold person doubles this range to 120 feet. However, the restriction placed on an upcast hold person that the targets must be within 30 feet of each other is not the range of the spell, rather, it is part of the spell's effect. Indeed, the rules for Casting a Spell state:
Each spell description in Chapter 11 begins with a block of information, including the spell’s name, level, school of magic, casting time, range, components, and duration. The rest of a spell entry describes the spell’s effect.
Here we observe that a spell's range, and the spell's effect are two distinct features of the spell's description. The range is given in the "block of information including the spell's name, level, school of magic, casting time, range, components, and duration", and the spell's effect is in the "rest of a spell entry". In the case of hold person, the effects when upcasting are a part of this "rest of a spell entry", which is distinct from the spell's range. So it does not interact with Distant Spell, since Distant Spell only interacts with the spell's range.