ひとつには…ためである => Partly because of ... N3
Cause, reason
ひとつ => A little N3
Repetition, habit
…ひとつも…ない => cannot possibly be ~ N2
Evaluate
もうひとつ…ない => (not) anymore N2
Description
... ひとつ…ない => nothing/not at all… N2
Emphasize the negative meaning
…ときたひには => when it comes to N2
Story topic
ひとつまちがえば => Just (negligence) N3
Ability
なにひとつ~ない => nothing/not at all… N3
Invariant
ひととおりではない => Not as usual (is okay) N2
Emphasis on degree
ひとつ…できない => cannot do the bigger things N3
Ability
ひとり ... のみならず => not only…, not just… N2
Add
ひとり ... だけでなく => not only…, not just… N2
Add