Look back during the Percival Baxter Era, contrary to popular belief, Baxter wanted the state to buy land around Katahdin but Maine's government goal was to sell all public land so it could be put into productive use by private industry. It also reportedly helped that large landholders were very generous to the legislature. Baxter eventually decided he could not trust politicians and went ahead and bought it on his own. He endowed it and put in a decades long effort to have multiple legislative sessions accept his deeds of trust which was to keep Katahdin, "forever wild" out of the reach of the legislature. In his opinion as a politician was that he did not trust politicians to protect lands for the long term if the popular winds shifted.
Maine's economy up into the 1970s was directly linked to pulp and paper and logging and the owners of those firms wanted to own the land and the state made it cheap to own and hold. The companies were generous with leases and also on occasion outright sold blocks on land on lakes for camps. Their lands were open to the public and it seemed to work well.
When Bigelow was threatened with development, there was a big public demand to preserve it, but Maine government was not, it was a people's referendum that forced the state to buy it and put in a new public reserve land system that was supposed to be managed long term as wildland for the Maine people. Forestry was allowed on some of the parcels but any profits were retained in the system so it would not be regarded as a "piggybank: to be raided. This worked for few decades until a recent governor forced the public reserve land system to cut large amounts of trees and that money went to the general fund despite the rules in place. The legislature recently did it again allowing an easement to be sold across forever wild lands. Thus, the Maine government seems to just not be the best entity to hold conservation land for the long term as short-term expediency seems to override long term commitments every time.
The combination of the spruce budworm epidemic in the 1970s and the long term effects of the clean water act where large corporations starting with Great Northern decided they could make money elsewhere, either in the southern US or foreign countries. Successor firms came in and when they needed money they cashed in the woodlands, GNP, Sappi, Fraser, Mead and IP all got of the land game and sold to investors who may or may not be in it for the long term and also considered recreation access something with monetary value. Right now, there is bit of lull in the demand for wood products but the planned multibillion dollar bioproduct refinery at Loring is an indication that there could be an upswing in demand.
The alternative to state control of wildlands has been the use of third party easements held by regional and national non profit groups ha been used extensively in Maine. Talk to anyone looking at the biggest controllable threats to the conservation lands and that is fragmentation of land. Once land is subdivided and goes into divided ownership, its difficult to manage landscape sized blocks, therefore the number one priority is lock up the development potential of land. Landscape blocks of land can be protected on a willing seller willing buyer basis. Generally, hand in hand with development rights is at least some form of sustainable forestry restrictions. Even though pulp and paper is vastly diminished in the state. forestry remains a source of employment in rural areas so outright banning of forestry on large blocks of lands would not be politically acceptable, even the Nature Conservancy and the AMC practice forestry on some lands they own in Maine. The nice thing with third party easements is they are somewhat independent of political influence, and if the third party is not doing their job they can be taken to court. Yes, not having state wilderness land upsets the Maine Woods National Park and the Restore the North Woods preservationists but I feel private landholders being reimbursed to sell off conservation and development easements makes the most sense for Maine as Maine long ago squandered their public lands that came along when it split off from Mass.
When I look at this map
Map it looks to me that there are a lot of large blocks of land being protected "forever" (until the next glacier) in Maine, it just is not publicly owned land. Note that the map excludes a few other entities like Bayroot owned by a Yale University. Its effectively managed as forest land but Bayroot tends to hold the land unencumbered by long term easements and then sells them piecemeal to other groups when they need some revenue for the Yale endowment. Add in those blocks and the map gets a bit darker. I believe John Malone's lands are the same although he really has no need for revenue.