It's very likely the human race will vanish much earlier than that, but OK.
The same way it was explained for the 9.7 billions of years of its existence before our solar system was formed. The universe exists independently of the human existence, consciousness or understanding or explaining of it, whatever the last two terms mean.
There are about a dozen of erroneous assumptions you're making in every 3 or 4 words in the above comment.
Was the universe a lifeless void of rocks and fireballs before Earth was formed? If it was, then that lifeless void of rocks not only may have created a vast number of other Earths in this or other galaxies, but it can also create a vast number of Earths after Earth is obliterated by the Sun.
When contemplating universal reality, one has to be able to step outside the bubble of their own impression of existence and look at things from an objective standpoint that does not depend on humans as a necessary part of any explanation they come up with about the universe.
The term "why", like all human language, is vague and its meaning depends on other contextual information. Are you looking for your own personal emotional gratification from an answer to this question? Is your question scientific in nature, and refers to the universal processes of existence? More often than not, people seem to be exasperated that we don't yet know the answers to everything. Only a few years ago people thought that having a headache meant that evil spirits were occupying one's head and they would puncture the patient's skull to let the evil spirits out. Your question seems to be in the same category of expressing dissatisfaction that there is yet a lot left for us to know, discover and figure out.
Beneficial is another of those vague, subjective terms that may not mean anything at all. Biological life as we know it, is part of the universe. If you're wondering what's beneficial about it then you suppose that the universe has self-centered interests, like humans have.
Now it is believed the universe will continue to expand to the point of oblivion.
It's not "believed". Cosmology is not a religion. It's theorized with substantially reasonable arguments to back it up. We may discover something in the next 1,000 years that may change our theories about the ultimate fate of the universe. It doesn't look like that''s likely, though.
It depends on what "good" means. It won't double the balance of your checking account, so it's not good in that respect.
We can only speculate about the universe at this point, but the certain thing is that human concepts of good, bad, useful, wasteful, interesting, important, etc, are all irrelevant to the universe, as is human existence itself.
A somewhat relating analogy is to think of a butterfly that has a life span of a few weeks, landing on a branch of an oak tree that has a life span of 600 years, and the butterfly thinking that the oak tree is dead, because in the few days that it has been landing on the same spot, nothing on the oak tree branch has changed.
