Not even vaguely surprised. This have been mooted before by another former spy Yuri Shvets.
It certainly makes sense given Trump's actions. Especially his push to help Russia install a pro Putin puppet in Ukraine and his attempts to weaken Europe.
I've always wondered if the first dossier was a Russian plant designed to be discredited and seemingly exonerate him of being a russian agent prior to his first presidency.
It also makes Putin's interference in US elections seem even more targeted when you view it as not purely disruptive but actually installing a Russian asset as president.
On balance it seems likely to be true. Surprised there's not more about it on Mumsnet