Withdrawing from the ABM Treaty was an early Bush blunder, but it is one whose costs we continue to pay even now.
When we discard treaties, as we have done since our nation's founding, one can only imagine what we are doing in the shadows--treaty or not. We've been exposed enough times from these covert actions that I can't imagine why any nation would give us even an ounce of credibility in any diplomatic negotiation. I'm all for diplomacy, but we are indeed an unreliable partner in that regard--to our detriment and the world's.
“… withdrawing from the treaty was done to expand the development of a technology that is one of the biggest boondoggles in recent history.” That is precisely why it was done. To enrich the huge military contractors that profit from this boondoggle. No other explanation makes any sense, as you point out.
In our current polarized climate, it has become obvious that the US simply ignores its treaty obligations. This has been true since Europeans landed in North America, and it is true under both of our marketing cartels disguised as political parties. The day after the JCPOA was signed, the Obama administration violated the treaty and never lived up to its obligations.
It seems extremely foolish for any nation to attempt to negotiate any agreement with the US, even if the US believed in diplomacy, which it obviously doesn’t. Diplomacy requires some mutual respect and that is beyond the capability of the Blob.
IIRC, the risible justification that the Bush Administration gave for placing Patriot missiles in Poland was "because Iran".