That is not true.
They concluded that what Trump and the Russians did did not meet the legal definition of collusion.
This was largely because no one ever thought to pass a law against something that was so obviously disloyal.
The evidence of a coordinated conspiracy is, in fact, widespread and very very well documented.
Trump had Paul Manafort, who was Moscow’s man in Kiev,as his campaign manager.
It is very well established that Manafort passed secret internal Trump campaign polling data to Moscow so they could measure the effectiveness of their disinformation.
The campaign could not be indicted for thier collusion with the Russians over the use of the material that Moscow had hacked from the DNC servers, because the Trump operative, Roger Stone, was not officially part of the campaign. None the less, he was key in both the selection and the timing of the use of such leaks, which were handled by Moscow’s man, Julian Assange.
Of course, Trump invited Russian intelligence agents into his campaign headquarters in the middle of the campaign to not collude, At least that’s what the Trump cult tells itself.