Learn Turkish: Her birey bu çeşitliliği özümsedi. - Every individual internalized this diversity.

The root is the noun öz (essence, core, or self). The suffix -(ü)mse is used to derive verbs that describe an attitude, internal perception, or treating something in a certain way. By adding this to öz, we get özümsemek, which literally means to make something a part of your own essence, hence "to internalize" or "to assimilate". The final -di is the simple past tense.

Break down the word çeşitliliği. Why does it have a ğ?

It starts with the adjective çeşitli (various or diverse). Adding the suffix -lik creates the abstract noun çeşitlilik (diversity). Because "this diversity" is the specific direct object of the verb here, it requires the accusative case suffix -i. When a vowel suffix is added, the final hard k of the noun softens into a ğ, resulting in çeşitliliği.

Why isn't the plural suffix used on birey (individual)?

In Turkish, the determiner her (every or each) is always followed by a singular noun. Even though you are referring to a large group of people collectively, you must say her birey (every individual) rather than using the plural suffix.

Is özümsemek only used metaphorically for abstract concepts like diversity?