Why can humans speak and think if apes millions of years ago could not

And why can other evolved creatures not talk or think?

First, let's please get this straight. Human beings did NOT evolve from apes. This is perhaps the most frequently mangled principle in all biology. Human beings took a different evolutionary path from apes and other primates, and the ability to vocalize in language was one of the biggest boosts to human evolution ever, along with the opposable thumb.
Making distinct sounds to communicate is not unique to humans. Many marine mammals such as dolphins have a complex series of clicks and whistles which communicate with others of the species, and humpback whale 'song' is still not fully understood but is known to be a method of communication. Many mammals have some sort of vocalization ability, such as your dog barking in different ways depending on alert barking to barking from excitement anticipating your arrival home or a treat.
However, humans are the only species that evolved complex language, the formation of specific sounds into words and thoughts turned into language. It is part of our evolutionary path and has nothing to do with what apes do or did; they are NOT our direct ancestors. Please understand that.
Putting our higher thoughts into a language is what sets us apart from all other higher mammal species on this planet, and the human brain is remarkable this way. Ape evolution took an entirely different path, and they obviously never developed this function, although we know that a few gorillas have been taught some basic sign language, but they cannot vocalize their thoughts, at whatever level they might be, into words and coherent language. That is a human trait solely, and is one of the main reasons that human beings are at the top of the evolutionary ladder.

Speech is a matter of vocal cord structure - humans have vocal cords that allow them to speak, most other mammals do not - by chance red deer that are not closely related have a similar structure. Human vocal cords are a result of evolution.