Two undersea cables in Baltic Sea disrupted

So what's the solution ? Assign a surveillance UAV to every Russian ship parked "without a good reason" over a cable ? It would be expensive, but doable, and create a reserve of vehicles for wartime use.

The solution is to project strength and hit them where they don't expect. You are dealing with a thug, not a cost/benefit accountant, as Obama seemed to mistakenly believe. As long as they do things and we respond, nothing good will happen. They have already calculated the response and found it acceptable. Instead of this, go to the mattresses. Oh, your bridge has suddenly exploded? Shame.

"We" won't respond because "we" just elected a Russian asset and he is going to install more in his cabinet.

It's already been settled that the trump dossier from 2016 was a work of fiction.

Why did Putin take crimea under Obama's watch, parts of Ukraine under Biden's watch, but then not make any huge moves like those while his "asset" was in the white house?

Because he needed all that time (2014-2022) to build up his forces and cash reserves.

Also, he needed a green light. Which was provided in the form of the chaotic Afghanistan pullout in 2021. Not that he was counting on it -- but once it went through, it seems very likely that tipped the scales in his mind in favor of deciding to actually go through with the full-scale invasion in 2022.

Its also been widely reported that when Trump first met Putin he said if he invaded Ukraine, he would turn Moscow and several other cities into a parking lot. Trump in several interviews has said he warned Putin not to do it, that he would pay a very, very heavy cost and he would see to it that he would.

This is all Trump had to do.

He was able to leverage the media's reporting on him that he was reckless, dangerous and prone to rash behavior and they were convinced he was going to start WWIII with? Yeap, you guessed it, the Russians. Putin believed what the media were reporting because Trump himself had verbally warned him.

He didn't need forces and cash. He did what OP recommended, he threatened Putin with force and Putin complied and just waited out Trump. It was a gift that Biden was elected in 2020 and if you go through the news reports, literally months after Biden was elected, Russia started massing troops on the border and readying their troops to invade. Its a strange coincidence that they didn't invade in the four years Trump was in office. He leaves and less than a year later, Russia is preparing to invade? C'mon man.

Your timeline is completely wrong.

- Biden's inauguration took place on January 2021.

- The Russians were amassing troops by December of 2021 (less than a year after he took office).

- The Afghan pullout wasn't until the Summer of 2021

- The Russian officially invaded in February of 2022

The green light wasn't needing forces and cash built up, it was Trump leaving office. The Afghan pullout had no effect on when they were going to invade since they were already massing troops and air support to the border regions where they finally launched their invasion from. Its not like the Russians decided to invade during the Afghan disaster as you insinuated, the invasion plans were already established by then.

Again, the tipping point was Trump leaving office.