Of course unusual weather events, natural disasters etc will play with conditions. We had a huge ice storm here a few years back, any course with poa greens lost them . A 100 year old , top Canadian private course just down the road from me lost every green and 400 mature trees. They rebuilt and put new grass in them all. Im sure insurance covered much of the cost but nonethe less a trmendous expense and loss of the greens for 2 seasons. We've also had a few crazy rain storms pastbtwo summers and a number of courses with rivers had banks overflow and flooded, holes lost, but they come back, good as new.
To my earlier point, in the absence of these unique events, its 100% due to courses not spending and doing what is required. Courses cutting back on conditioning have 1 foot inn the grave and wont last, especially if there are other options. Up here in my area , which is largely populated less than 3 % of pay as you play courses turn a profit yet they are typically very well maintained. Lots of demand so if a course gets identified as being in poor condition on a local forum, it will suffer with reduced play. My buddies private course is also a top rated track and suffered with bad winter kill on 3 holes and a new greens super who wanted to rebuild the greens for better reception amd longeavity ( they were pristine before but very hard and fast and hard to hold being a windswept links course) the process took 2 + seasons..they lost a significant number of longstanding and great members who left for greener pastures.....with a $15-20 thousand initiation amd $6000 annual dues , they wouldnt stand for it.
If the economy of an area is lacking or Demand has lessened for whatever reason, courses will wither and cut back until they die, happens everywhere . Thankfully the reduction in people playing golf that we have witnessed the past 20+ years ( globally) has stabilized, so the worst is hopefully over
When I play a strange/new course, the first two things I look at are course scorecard and ratings and reviews of conditions .