Crudely speaking, industrial R&D has three phases: proof of concept, de-risking, and manufacturing. 7LP might (or might not) have passed the proof of concept stage. De-risking is usually the hardest stage (such that many people don't even consider it a stage, preferring to break it down into smaller stages). It is highly likely that this is where they decided to cut bait. (Incidentally, de-risking is usually heavy opex in the R&D department whereas HVM/NPI is mostly heavy capex; while "just" an accounting trick, this can be significant in many companies, and create a real barrier if the necessary opex spend is not palatable.)

The reason one would expect 7LP to be cheaper to launch now is that their competitors have got equivalent processes into production that can be learned from, or even "learned from" (ripped off). Equipment suppliers have debugged their offerings and pruned their lines to what's useful. In short, someone else has derisked it and found what works. That is a major advantage. In other industries, one company doing the derisking can launch an entire industry (see, Apple, iPhone) if moats are low. Moats are very, very, very high in the foundry space, so there are not many companies that could copy TSMC 7FF or Intel 7 even if they wanted to. GlobalFoundries could do it. But they choose not to. If they were on the cusp of a node introduction, they'd love to see their competition swoop in and solve the last problems for them. Sure, it makes them late to market, but at a vastly lower total spend to enter the market (one with tremendous moats and limited competition!). They could probably profit off that.

But they don't want to. So, either, leading-edge process nodes are uneconomical (in which case, good riddance, leave the market), or they don't actually have significant R&D effort completed and are still billions of dollars in R&D opex away from having anything viable. In which case... nothing of real value was lost.

So, yeah, it sucks that we lost a competitor. But I don't think we lost GF on the leading edge because they didn't like the color of paint on the new ion-implanter's frame. I think we lost them because they didn't have a product and they knew it. In which case there is nothing to mourn.