Ağır iş yükü tükenmişliğe yol açtı.

Because the expression yol açmak normally takes the thing it leads to or causes in the dative case.

So:

• tükenmişlik = burnout / exhaustion
• tükenmişliğe = to burnout / into burnout / leading to burnout

In this sentence, yol açmak means to lead to or to cause, so the dative ending is required.

This is a very common Turkish sound change called consonant softening.

When some words ending in p, ç, t, k take a vowel-initial suffix, the final consonant may soften:

• p → b
• ç → c
• t → d
• k → ğ or sometimes g

So:

• tükenmişlik
• tükenmişlik + e
• becomes tükenmişliğe

This happens because the suffix starts with a vowel, and Turkish often smooths the transition between sounds.

That is because of vowel harmony.

The dative suffix has two forms:

• -a
• -e

Which one you use depends on the last vowel of the word. In tükenmişlik, the last vowel is i, which is a front vowel, so the correct dative form is -e.

So:

• ev → eve
• okul → okula
• tükenmişlik → tükenmişliğe

Yol açmak is a common Turkish expression meaning:

• to lead to
• to cause
• to give rise to

Literally, it means something like to open a road/path, but in many sentences it is used figuratively.

So in this sentence, it does not mean a physical road. It means that the heavy workload caused or led to burnout.

A useful pattern is:

• X, Y’ye yol açtı.
• X led to Y.

Açtı is the simple past tense in the third person singular.

Breakdown:

• aç- = verb stem
• -tı = past tense ending

So açtı means opened, caused, or led to, depending on context.

Why -tı and not -dı?
Because the verb stem ends in ç, which is a voiceless consonant, so the past tense suffix appears with t instead of d.

Compare:

• geldi = he/she/it came
• açtı = he/she/it opened

Here the subject is Ağır iş yükü, so açtı means it caused / it led to.

Because Turkish is usually a subject–object/complement–verb language, unlike English.

This sentence is structured like this:

• Ağır iş yükü = subject
• tükenmişliğe = complement in the dative case
• yol açtı = verb phrase

So the verb naturally comes at the end.

This is one of the biggest word-order differences between English and Turkish.
English: Heavy workload caused burnout.
Turkish: Heavy workload burnout-to caused.

That word-for-word English order sounds strange in English, but it is normal in Turkish.

İş yükü is a noun compound.

It is made from:

• iş = work
• yük = load, burden

Together, iş yükü means workload.

In Turkish noun compounds like this, the second noun usually gets a special ending, often called the compound marker or third-person possessive suffix:

• iş + yükü
• not just iş yük

That is why you see yükü rather than plain yük.

Other examples:

• su bardağı = water glass
• okul kapısı = school door
• iş yükü = workload

Yes. Ağır literally means heavy, but like English heavy, it can also be used figuratively.

So:

• ağır çanta = heavy bag
• ağır iş yükü = heavy workload

Here it means something like:

• intense
• burdensome
• demanding

So this is a very natural Turkish phrase.

No. It is not a direct object.

It is a dative complement required by yol açmak.

A direct object in Turkish is usually marked with the accusative when definite:

• kitabı okudum = I read the book

But here, tükenmişliğe has the dative ending -e, because the verb phrase is built with yol açmak + dative.

So the structure is more like:

• lead to burnout rather than
• affect burnout

That is why you should not think of tükenmişliğe as a normal direct object.

The Turkish letter ğ is often called soft g, but it usually is not pronounced like a hard English g.

In many cases, it:

• lengthens the vowel before it, or
• creates a smooth glide between vowels

So:

• ağır sounds roughly like aa-ır / aa-uhr
• tükenmişliğe is pronounced roughly like tü-ken-miş-li-ye or tü-ken-miş-li-e, depending on the speaker

Also note:

• ü is like the u in French tu or German über
• ı is the Turkish vowel with no exact English equivalent; it is a relaxed, unrounded vowel

You do not pronounce ğ as in English go.

Because Turkish does not use articles the way English does.

There is no exact equivalent of the, and although bir can mean a/an, Turkish often simply leaves it out when the meaning is clear.

So:

• Ağır iş yükü can mean a heavy workload or the heavy workload, depending on context

Turkish relies much more on context than English does for this.

That is why the sentence sounds complete even without any article word.