Given that it was 1700s and the presence of a Son was considered paramount for succession, and the Salic law, in effect at that time barred women from inheritance, Charles VI was the last male heir to the throne, unless Charles VI had a son.
Which he didn't.
But he had 2 daughters, Maria Theresa & Maria Anna. Realizing that his kingdom would be divided on his death, he decided to change the law, and allowed his daughters to inherit the kingdom
Which was pretty sad for thhe daughters of his elder brother, Joseph, who he disinherited
Every other European power was smacking their lips in anticipation, of devouring the wonderful Austro Hungarian empire as a sweet desert, as it's division was imminent.
Things came to head in 1740, when Charles VI died and Maria Theresa became the Empress of Austria.
Half the Europen powers, Like France, Prussia and Spain, sided with the daughters of Joseph, because they wanted to takeover Austria
Britain, Dutch and Russia, sided with Maria Theresa.
This resulted in an 8 year war called the war of Austrian Succession, in which 3,00,000 died
Unfortunately, when the war ended in 1748, nobody was happy with the terms. As a result, in 1756, Everyone went to war again, in the Seven Years war.
This is where Things begin to get interesting.
As a part of the Seven Years war, England and France took opposite sides in a country, far away from Europe, where they were just getting their foot in.
The country was India.
First they started supporting local rulers against each other.
Then they dropped their pretence.
Things came to head, when French and British fought the Battle of Wandiwash in 1760.
Unfortunately for the French, they were annihilated.
British captured their Capital Pondicherry and Chandranagar in Bengal and French were effectively booted out of India.
Which did not go well with them and they were waiting for an opportunity to give England a bloody nose somewhere.
That opportunity came in 1777. In the United States of America.
French went all in on that one. So much so, that 75% of the US army's gunpowder, was French.
They even blockaded the American coast, so that no British ships reach out for help.
As a result, British went thru a humiliating surrender in Yorktown, and America was born.
Which made the British double down, in their other colony, India.
They put all their effort and focus to subjugate India, lest it become like America.
And because the local Indian rulers, could not turn to a European power like France for Support, the Brits succeded.
To summarize,
The Austrian King couldn't produce a male heir, which resulted in a war between France and Britain, which ensured India was colonized and America became independent.
