To have a holistic view of this matter, let’s go back to the beginning.
1969 was the year when Project Management Institute (PMI) — the world’s leading professional organization for project management– was founded. Professional Project Management now has educational and certifying body. Millions of memberships followed… around the world! PMI’s book, Project Management Book Of Knowledge (PMBOK), 
is so popular…it has been translated in major languages… and millions of copies sold worldwide. Project Management is engrained to people and organizations worldwide.
Going into year 2019, that is 50 years of professional project management engrained in people’s minds and their respective organizations. Name any industry… they do waterfall/ predictive approach. They fund projects and deliver value via projects! 
Industries like construction, medical, technology, banking, education, research, manufacturing, etc.
Resources fluctuate based on demand as dictated by the project’s scope, cost and schedule. The famous iron triangle.
I am a civil engineer…I come from the construction industry… where PERT/CPM is a must have tool… to make certain that the delivery of value is on budget, on time, and on schedule. Civil Engineering industry needs a very predictive approach to delivering value. I totally understand this mindset — in fact, I am also a PMI PMP certified– and I have embraced this predictive approach like most folks… it works … and proven to work for — at least — the past 50 years!
Waterfall is already tightly hardwired and engrained … to a lot of peoples’ minds and organizations’ DNA. 
Also, add lean six sigma to this predictive project Management approach… now we have lean-waterfall project management! This tandem kept the Agile mindset at bay for a long time. We saw Agile’s rise and fall in the last two decades …and now, we are experiencing its resurgence.
Recently, the lean-agile (not just agile) mindset is becoming popular … specially to large corporations. 
This is due to SAFe, I surmise (it can really scale up — compared to other Agile frameworks — holistically to large corporations’ needs). This lean-agile mindset — regardless of the Agile framework that is used — is very different from the waterfall mindset … it is a 180 degrees difference — like day and night! Therefore, to implement this effectively, a mindset shift is needed — a must have — if one ever truly goes / transforms from waterfall mindset to lean-agile mindset.
This lean-agile-required mindset-shift includes the SAFe-espoused funding model shift: fund value streams, not projects.
Let’s look at — albeit cursory– this SAFe ‘Funding Model’.
To be continued.
