That's kinda what the deal is about, tho:
1. Ukraine gets rebuild, the US and Ukraine own huge portions of Ukraine's new industry through the fund
2. The fund gets richer and richer with Ukraine slowly taking over management, the US retaining a minority portion
3. Russia attacks Ukraine, captures all of it
4. Nearly all remaining industry and rights to natural ressources are retained by the fund, managed by Ukraine's exile government
5. Russia wants to expropriate the fund to cut off the funding available to the exile government
6. Russia realizes they'd have to expropriate the US government, starts sweating
7. Russia wakes up and decides not to proceed with step 3. to 6., because the downsides of taking over a country (insurgency, tons of explosives everywhere, new huge portions of population on expensive welfare and healthcare, ...) aren't worth it without any of the upsides.
> Issue is about not having any security guarantees.
Because they're not even negotiated yet. The "minerals deal" is something the US and Ukraine can negotiate right now, so it's on the table.
For all the other stuff Russia and Ukraine need to come to the same table, which Ukraine is very reluctant to do.
Trump only tried to get Ukraine to agree to a bare minimum ceasefire, to stop the killing.
Everything else is up to negotiations afterwards.