“Another mendicant’s mind is seized by restlessness to realize the teaching. But there comes a time when their mind is stilled internally; it settles, unifies, and becomes immersed in samādhi. The path is born in them. They cultivate, develop, and make much of it. By doing so, they give up the fetters and eliminate the underlying tendencies.”
The above is the fourth path mentioned in SuttaCentral
Q: How is this 4th path different from the 1st (serenity first and then discernment)?
When they’ve been given up and eliminated, only thoughts about the teaching are left. That immersion is not peaceful or sublime or tranquil or unified, but is held in place by forceful suppression.
But there comes a time when that mind is stilled internally; it settles, unifies, and becomes immersed in samādhi. That immersion is peaceful and sublime and tranquil and unified, not held in place by forceful suppression. They become capable of realizing anything that can be realized by insight to which they extend the mind, in each and every case.
Seems like restlessness (too many thoughts, agitated mind) is so strong that it prevents them from attaining samadhi, and when that barrier is overcome they’re able to attain Arahantship, whereas as other people are able to quieten their mind and attain samadhi early on in the training and enjoy the fruits gradually. Bahiya Barkcloth comes to mind, some sources say he attained Arahantship all at once (i.e. from Puthujjana straight to Arahantship).