Plenty of large companies have over-reached themselves with mergers or acquisitions of smaller companies, property or other assets even though their long-term balance sheets are weak, and many big names have gone on to fail shortly after doing so.
So again, just because the org may make an apparently sizeable purchase here and there, doesn't mean they are on solid financial footing.
If they are sensible, what they will do with this land purchase is use some of it for rental income, perhaps by leasing it for property development. Too often they've just purchased land for their own use, which is fine as a held asset, but has no real value unless and until it is sold, at which point it only generates a one-off income anyway. The real win is in generating a regular return, and the best chance of that is with leasing of land or property for commercial or residential use.
Also, in terms of long-term finance, if this is to build an assembly hall - as it seems from the info at https://jw-longisland.org - then it's probably with the intention of saving money on renting expensive corporate facilities in future (and possibly closing and selling off nearby kingdom halls).
Perhaps those who believe the org wants to move to being more like a 'mega-church' with a small number of large facilities rather than lots of smaller halls - at least in the USA - might be right after all? All those dozens of small, ageing halls must be building up a serious repair and maintenance backlog, which depends on a dwindling number of congregants to support with their voluntary labour. Better to centralise more, sell off those burdensome properties and merge remaining congregations. A smaller number of large congregations would also be easier to control, to spread the falling number of appointed men among, and would enable the org to cut the number of circuit overseers too.