Assume the following theoretical scenario:
You have a large number of existing RIPE, ARIN, APNIC ASes which will take any ipv4 resources they can get. They're all on waiting lists or have been informed no new blocks will be forthcoming.
240/4 is something like 256 million IPs.
Let's say that the global benevolent ipv4 dictator decides that each ISP, MNO or other waiting list entity gets a single /16, one time only.
That's 64,000 IPs per corporate entity. Not actually very large at all on the scale of regional mid sized operators with 300,000 last mile broadband subscribers, or mobile network operators, nevermind top-10-size DOCSIS3/GPON/DSL last mile operators that have many dozens of millions of customers. One /16 is a tiny drop in the bucket compared to the demand for IP space for indivudual-customer DHCP pool usage by an ISP the size of Astound or a South Korean GPON operator or similar.
That's 4000 entities which each get their one time /16 and then 240/4 is entirely exhausted.
Unrealistic? Halve it so that each network operator waiting for IP space reources gets one/ 17, one time only, I would still bet good money that there's 8000 ASes out there that right now would happily take their "free "single /17 , and you'd still have immediate complete exhaustion of 240/8.