How did it happen that there are two different words "insulation" and "isolation" for virtually the same concept? [closed]

The -atus ending insasmuch as it is formed from the past participle of the verb (and thereby conveys the idea of action-done-to) is suited to the meaning "protected by means of a barrier"; the earlier borrowing from Latin insulanus (Middle English insulan, island-dwelling) shows an adjectival ending appended to nouns to convey the idea of origin or possession.

The insul-- form was already here since the mid 15th century.

The Middle English concept of "island-dweller" already went beyond the geographic definition to include the more abstract idea of not being subject to certain forces or influences:

Eke, for he is a insulane, therefor he doth no subjeccion onto no man.

The idea of "being shielded from" is lurking there.

The Latin-derived -ate ending was already productive in Middle English technical/scientific writing in the first quarter of the 15th century.