I used "easily provable" because the originally document contains very specific facts related to travel of those involved which should be documented if they used an airport that requires a flight plan with the FAA. Is that not the case?
As far as your assertion that agencies deemed this "worthy of escalation," that's simply not what happened. You make it seem like they have been investigating this for months and found some new revelation. Nobody knows if that is true, and odds are not for or against that assertion. Is that what you think happened, ie: that the intelligence community has been investigating this and decided that because of new evidence they decided that it needed to be presented to the PEOTUS at this time?
As for my personal opinions....I guess my belief is that this document(32pg) was making the rounds and it was politically combustible due to the synergies with the russian stories of recently and that intelligence agencies decided they needed to include it in the briefing if indeed they were investigating it, just in case they found something.
IMHO, the primary reason it is a big story today is because the information from that classified briefing leaked. I don't think any new evidence has or will spring up concerning it and in fact I believe that now that it is finally being investigated by a legitimate intelligence agency and a proactive media it will be largely debunked in rather short order. Either way, the only way anything happens here is if an intelligence agency proves Trump's proactive involvement with Russia during the election, and that will probably be a longshot imho.