No. That would be a conspiracy theory.
And beyond the miniscule amount in ad spending, you also have to accept that a small number of political ads on Facebook swung the election in the States that Clinton lost.
If there's one constant in the investigations, it is the steady drip of new facts. In fact, it is self-assured reactions like the above that have destroyed a lot of people's credibility on the topic.
That's just speculation. We can only base rational discussion on the information available to us now.
At that rate, even if the Russians ads we're discussing had all been targeted at the Presidential election in those 3 states (far from true), that only equals about 5,000 votes.
Further assuming that 2/3's of votes aren't changeable and the $2.5 billion was spent to influence the remaining third, we're talking about 1500 votes influenced.
And I brought up credibility because one important facet that seems to be serially forgotten is that the major targets of the investigations have already destroyed their credibility, as have many commentators. I would encourage some googling to look at the past claims people make - more often than not you're hearing assertions of tribal fidelity rather than arguments based on factual exploration, and one bit of that information available to us now is a fair amount of background on motivations.
> We can only base rational discussion on the information available to us now.
This is false. We are planning animals. We do what-if projections constantly. In fact, we can't not do it - you did it yourself to make an implicit argument above attempting to make any forward-looking seem silly.