The number of earned doctorates in 2017, according to the NSF, was 54,664 (https://ncses.nsf.gov/pubs/nsf19301/). Approximately 50% of those graduates expect/want to teach at the higher education level. The number of doctoral graduates who want to teach far exceeds the number of positions, and colleges and universities are (logically) taking advantage of that fact.
Whether a college or university is for-profit or non-profit, finance is always a core value. If they can hire part-time adjunct faculty "as needed," with no expenses for benefits, the accountants see no reason to hire full-time faculty.
Additionally, by using primarily part-time faculty, colleges and universities can select those individuals who best fit student demographics and accreditation requirements, while also making adjustments as needed.
I am an associate/adjunct faculty member who was full-time. The demands on my time and participation in non-paid activities is still high. Many adjuncts work at several universities while maintaining a full-time job elsewhere. There can be no loyalty in such a situation, so everything breaks down to dollars and cents. Where I teach, adjunct faculty are paid per class, and the rate has not changed in a decade.
Highly qualified faculty who tire of getting 2-3 classes a year, while being required to attend quarterly "faculty" meetings, dealing with administration email proclamations on a regular basis, are finally saying "enough is enough" and quitting. However, the universities really do not seem to care as more and more universities opt for the part-time adjunct model.
This articles states this issue is a "ticking time bomb," but I do not see that. Financial factors are the driving force and accountants are making the major decisions, but they can quickly adjust as needed as there as an excessive number of faculty who would jump at teaching "just a little more."