OK. I think you analysis is more-or-less on the mark. Putin definitely felt emboldened because of the weakening bonds among the western nations, thanks to Trump. That is for sure.

Nope. Were this true he would have moved when Trump was actually President, and not waited until the supposedly-stronger-alliances-guy in Biden showed up.

Your analysis overlooks that Putin already took Biden's measure when he was doing what he wanted in the Crimea when Obama was President and Biden was his VP. He knew darned well that Biden's first instinct is to hesitate when decisiveness is called for; that's been a trait of his for literally decades: He thinks of himself as a master diplomat, and mistakes indecision and delay for "thoughtfulness".

Nothing to do with Trump, sorry.

The second point you get wrong is here: The obstructionism in Congress by a minority (Republicans) to send weapons to Ukraine . Trump sent weapons to the Ukraine, were you aware of that?

Associated Press: US agrees to send lethal weapons to Ukraine, angering Russia
WASHINGTON (AP) — The Trump administration has approved a plan to provide lethal weapons to Ukraine, a long-awaited move that deepens America’s involvement in the military conflict and may further strain relations with Russia. Moscow responded angrily on Saturday.

The new arms include American-made Javelin anti-tank missiles, U.S. officials said late Friday. Ukraine has long sought to boost its defenses against Russian-backed separatists armed with tanks that have rolled through eastern Ukraine during violence that has killed more than 10,000 since 2014. Previously, the U.S. has provided Ukraine with support equipment and training, and has let private companies sell some small arms like rifles.

That bolded bit will be important in a minute. The narrative of 'Republicans helping Putin and not wanting to arm Ukraine' does not and never has held any water.

Bbbbut Biden opened the floodgates.

Or did he? What's his actual history with giving the Ukrainians weapons? Let's go to 2021:

nbcnews.com - Appeals ukraine biden admin holds back additional military aid kyiv di

The Biden administration prepared a $200 million package of additional military assistance for Ukraine in recent weeks but held off on delivering the aid despite appeals from Kyiv and some lawmakers, according to three people familiar with the issue.

What aid did he hold up?
foreignpolicy.com - US ukraine russia military support congress biden delay aid
The White House has not yet OK’d a package of lethal and nonlethal assistance for the Ukrainian military that includes Javelin anti-tank munitions, counter-artillery radars, sniper rifles, assorted small arms, and communications and electronic warfare equipment, according to a source familiar with the matter.

Why would he hold it up? Because Biden was always squeamish about "angering" the Russians, that's why.

He's actually been dragging his feet for a while; one just needs some sophistication to skip past the BS White House spin that they've always been on top of giving them everything:

cnn.com - Joe biden cluster munitions ukraine

President Joe Biden told CNN’s Fareed Zakaria Friday that it was a “difficult decision” to provide Ukraine with cluster munitions for the first time, but that he was ultimately convinced to send the controversial weapons because Kyiv needs ammunition in its counteroffensive against Russia.

Giving the Ukrainians cluster munitions is in no way "a difficult decision" when they're the ones keeping orcs from carrying off their children. If you get into a fight you fight to win, not something else.

We can count on the democrats to provide the "moral center" needed here though:
politico.com - Top dems break with biden over sending cluster bombs to ukraine

“The decision by the Biden administration to transfer cluster munitions to Ukraine is unnecessary and a terrible mistake,” said Rep. Betty McCollum (D-Minn.), the ranking member of the House’s defense appropriations subcommittee. “The legacy of cluster bombs is misery, death and expensive cleanup generations after their use.”

“These weapons should be eliminated from our stockpiles, not dumped in Ukraine,” she added.

Reeeeal lib of genius, that one. What about Republicans? Surely they opposed this, right? What did some of them say about cluster munitions?
cotton.senate.gov - Cotton statement on providing cluster munitions to ukraine
Washington, D.C.— Senator Tom Cotton (R-Arkansas) released the following statement after it was reported the Biden administration will provide cluster munitions to Ukraine’s military:

“For Ukrainian forces to defeat Putin’s invasion, Ukraine needs at least equal access to the weapons Russia already uses against them, like cluster munitions. Providing this new capability is the right decision—even if it took too long—and is one I’ve long supported.”

And surely they've never called for shipping advanced weapons there?

thehill.com - Gop senators ask biden to provide ukraine with missiles needed to win war

A group of Republican senators sent a letter to President Biden Saturday urging him to “immediately” provide the missiles Ukraine needs to win its war against Russia.

Sen. Tom Cotton (R-Ark.) shared the letter in a post on X, the platform formerly known as Twitter, arguing that not sending the weapons would “only prolong the war and cost lives.”

Cotton was joined by Sens. Roger Wicker (R-Miss.), Susan Collins (R-Maine) and Lindsey Graham (R-S.C) in his request.

“We … urge you to immediately send MGM-140 Army Tactical Missile Systems (ATACMS) to Ukraine,” they wrote. “Additional delay will only further undermine U.S. national security interests and extend this conflict.”

Step away from the narratives and look at the facts.