Malick isn't the best example here. Tree of Life was made for around $30 mil and his most recent, A Hidden Life was made for in the vicinity of $8 mil. In the context of our current blockbuster climate where the latest Bond movie costs upwards of $300 mil to make, I wouldn't call Malick's films "big expensive movies," and I certainly wouldn't compare it to Coppola's $120 mil+ price tag. Hollywood has shown that it will only give that kind of money to films that fit a strict, suffocatingly rigorous formula (i.e. existing IP, car chases, explosions, world-saving heroes, etc). It most certainly will not fund a project to the tune of seven figures based on an original idea that has been described as “a love story that is also a philosophical investigation of the nature of man.” If you don't have a remake or reboot of an existing IP, you're not getting funded, period.
Also Malick is a consistent awards contender in years where he releases a movie. Tree of Life is one of the most critically acclaimed films this century and studios like to invest in critical prestige when they can, given a reasonable budget. His movies also generally make their money back. This is also why networks will let TV shows like Crazy Ex Girlfriend and The Americans go on towards a natural conclusion, instead of canceling immediately, even if viewership is low. Coppola simply does not have that reputation anymore. In fact, I think he lost it all the way back in the early 80s. After Apocalypse Now, he failed to make a movie that captured unanimous critical favor like his string of hits in the 70s. Four of his last five movies have been largely panned. His 1996 flop, "Jack," is one of the worst movies I've ever seen and a lot of other critics agreed. A movie like that typically ends careers. He does not have the cachet to warrant an investment of $120 mill on an idea that appears at first glance to have dubious mainstream popular appeal. With that said, I would certainly see it.