How can you argue that equality is most important ideal in the declaration of independence?

It cannot be argued or supported.
The concept of liberty was fashionable in the mid-late 18th century. It was invoked in the 1789 French Revolution with its slogan of "Liberty, Equality and Brotherhood."
In the Declaration of Independence, it is used as political rhetoric. Cynically and dishonestly.
The Declaration and the entire strategy for Independence was a male affluent middle-class movement.
There was no equality in a situation of slaves, indentured servants, women, native tribes. None of these had any social standing, nor votes nor took part in any political process.

"Equality" was just demagogic language to attract mass following to a narrow and exclusive strategy.

[A modern recent equivalent could be, "Let's Make America Great Again." It has no meaning and no methods attached to it; but it attracts the support of a largely dispossessed population.]

I don't think equality was the most important detail in the DOI and I believe the signers knew it. How could they be declaring all men equal while slavery was legal? The Brits had a field day w/ that.
The most important detail is in the title ... "Independence". The colonists had had enough of the Brits messing w/ their lifestyle w/ measures like taxation w/o representation and quartering the redcoats.

The concept of "equality" as used in the declaration only refers to "equality" in it's legal sense; viz. that all persons are "equal in the eyes of the law" and does not, I repeat not, refer in any sense to equality of persons in any sense. ... As a matter of fact, the phase referenced was intended to emphasize the underpinning concerpt that all rights come from God and are not a gift of the State.

By thinking