The Ukraine NATO talks were the direct precursor to the Crimea invasion and were ongoing before that. Russia has black sea navy assets in Crimea and per NATO, Ukraine couldn't support Russian military assets in the country while simultaneously joining NATO. Russia needs them there, so they took Crimea proactively to preserve their naval position in the event Ukraine joined NATO.

>Russia needs them there, so they took Crimea proactively This is a weak argument. Why can't they build their own port on their own land?

It's not an argument, it is well documented fact. A cursory reading with any detail of the 2014 crisis will mention this. Russia has it's only warm water port in Crimea as per an agreement between Russia and Ukraine upon Ukraine's independence from the USSR. Ukraine joining NATO means Russia must withdraw from that port. This is militarily not an option for Russia, so you get the annexation of Crimea.