Why did Chandragupta Maurya and Chanakya attack the outer parts of the Nanda Dynasty first?

The entire pop culture story about the Emperor Chandra, the brahmin Chanakya, and the establishment of the Maurya Empire is pure nonsense. The story is not only improbable, it's completely implausible.

The story of the Emperor Dhana's assaults upon Chankaya's family is lifted almost entirely from the Puranas- but our Intellectuals won't accept it because “Puranas are all forgeries written yesterday by Hindu counterfeiters”.

The story of Chandra “taking over border territories” only makes sense if you're an intellectual with more degrees from big colleges than brain cells.

The most probable- and, I'm fairly certain, accurate- line of events is as follows:-

1- Chandra is a Maurya, a Bihari Kshatriya line who've obtained great power over the course of the Haryanka and Nanda wars. He's probably a general or governor of some province.

2- The Nanda Empire is overstretched, extending from the Iravati to the Godavari, and the unceasing wars have weakened administration and civic authority. Generals and Administrators are pissed off, so are the Citizens.

3- Chanakya, who's achieved a fair bit of notoriety for his… unorthodox ideas on the nature of Power, is popular among several discontent Lords of the time. I don't think he was actively whispering in Chandra's ears throughout though.

4- Chandra and his Allies stage a coup, have Emperor Dhana executed for tyranny or whatever, and declare the establishment of a police state on the lines of Chankaya's Ideal State. The Governors in the Provinces are either Biharis themselves and so kin to the Maurya or are Civilians who hate the militarism of then Magadha or just are fans of the Chankaya model.

5- Chandra, now Emperor, elevates Chanakya- the spiritual head of the new Imperial System- to the post of Prime Minister. Thus begins a Police State the likes of which India won't see again until the rule of the Overtyrant Jabberlal Neckscrew.

Such a rundown of events would make sense for the following reasons.

1- Classical India was arguably far more close-knit than even Modern India. The Elites and even the average Trader/ Soldier/ wealthy Farmer would've known Sanskrit or a common Prakrit. They all studied Astronomy in Gujarat, Politics in Punjab, Astronomy and Maths in Malwa, Theology in Andhra, Logic and Rhetoric in Bihar. All of them studied the same stuff, heard of the same scholars, and had roughly the same Weltanschauung.

2- The sheer speed at which the Nanda Empire transformed into the Maurya Empire is phenomenal. I don't buy that one after other BS for a minute. States have inertia and a life of their own. The Mauryas were, in all likelihood, “inheriting” the State instead of conquering it.

3- Institutional Power is EVERYTHING. A single person- like the outlaw Pop Culture pretends the Emperor Chandra was before his enthronement- is NOTHING. Anyone who tells you otherwise is either a child or a snake oil seller.

4 - The primary Institutions of the Nanda State- as with the Maurya Empire after it- would've likely been the Army, the Bureaucracy, the Brahmins, Independent Religious Orders, and Trade Guilds centred in the Provinces. Control over two would've sufficed to make one Emperor. Chandra appears to have had contacts with at least three. What sort of Outlaw is that?

Of course, Reality never makes for a good Story , and what is History but a set of Fables agreed upon by Children?