Google Sheets natively controls how the functions recalculate according to different behaviours (modifying cells, opening the spreadsheet, …) and we have no control over it. This is why you saw your functions recalculating and your data loading.
But fear not!
- To avoid that ImportFromWeb fetches the data source constantly, imported data are cached 1 week by default (and up to 4 weeks). You can increase the cache duration up to 4 weeks (see on this page how to manage the cache), so Google Sheets willl re-execute the =IMPORTFROMWEB() functions anyway but data will be retrieved from the cache and no credits will be used.
- You may add the hard_paste option as a 3d argument of the IMPORTFROMWEB function; it pastes the collected data as values directly into your spreadsheet, so you’ll never get a “loading…” again for an URL already fetched!