How tenses formed in french

Question

I've recently been studying the:

-Imperfect;
-Simple Future; and
-Conditional (mood)

in French, and I'm wondering why the tenses are constructed in the way that they are.

For the imperfect, one conjugates the verb as though it were a normal present-tense verb, but just uses different endings (-ais, -ait, -aions, etc.)

For the simple future, the verb stems are modified and always end with a least one "r" for the stem, then the conjugation for avoir is added (largely) to each form accordingly.

For the conditional, one takes the verb stem of the simple future and then adds the conjugations for the imperfect tense.

Why is there such a strange combination for the conditional and how did the other tenses come to be with their conjugations and stems and whatnot?

Answer 1

Conditional origin is already answered here: What is the historical origin of the French présent conditionnel?

Imperfect is a direct evolution of the same tense in Latin, with the noticeable fact an 's' has been added to the first person singular.

amabam   → amava   → ameie   → aimoie  → aimois   → aimais
amabas   → amavas  → ameies  → aimoies → aimois   → aimais
amabat   → amavat  → ameiet  → aimoiet → aimoit   → aimait
amabamus →           amiiens →                      aimions
amabatis →           amiiez  →                      aimiez
amabant  →           ameient →           aimoient → aimaient

Reference: http://monsu.desiderio.free.fr/curiosites/imparfait.html

The simple future has been designed a similar manner than the conditional, from periphrasis:

amare habeo   → amareo   → aimerai
amare habeas  → amareas  → aimeras
amare habet   → amarea   → aimera
amare habemus → amaremus → aimerons
amare habetis → amareis  → aimerez
amare habent  → amarent  → aimeront

As you see, its no surprise if you recognize the avoir verb in the future tense endings as that very verb was already used in Latin.

Reference: http://monsu.desiderio.free.fr/curiosites/futur.html