No, they had nothing to do with Russia's invasion in 2014 and they have nothing to do with it now. Putin made known his reason in his February speech before the invasion. He does not accept that Ukraine is an independent country. All else is but rationalization to justify what is, in truth, merely his attempt to reconquer Ukraine.
NATO expansion was not the cause. By its own laws, Ukraine could not join NATO as long as Crimea and Donbas were occupied by Russia. All the talk about Ukraine joining NATO was just that, talk. And Putin knew this. You are also discounting Ukraine's motivation for wanting to join NATO because of Russian threats, threats that became real with the 2014 invasion. If NATO expansion had been the cause, Putin could have easily negotiated Ukrainian neutrality in exchange for his withdrawal from Donbas and Crimea.
The Irony is that Putin could have just annexed the parts of Donbas that he occupied and it would have been an fait accompli. There would have been a lot of rhetoric from the West but there would have been no military aide to Ukraine to get it back. But Putin had to be greedy and tried to conquer all of Ukraine. It has not worked out as he had anticipated.