For one, Trump was already in charge for four full years. He never dared launch a military aggression against Iran.
Secondly, Trump is not one to trigger a large scale, open ended, extremely costly and years long conflict - it would go alienate his entire voter base. One of Trump's main campaigning themes was the need for the US to disengage from these sorts of conflicts started by his predecessors.
Thirdly, the US president is not the ultimate decision maker when it comes to issues as strategic and serious as these: the regime's deep state makes these decisions. If a president fails to toe the line, they will not hesitate to murder him, and in front of the cameras at that so as to bring the point across, e.g. John Fitzgerald Kennedy. Already, we have had top Pentagon generals such as Mark Milley publicly declare that they would have sabotaged the Trump administration, had it ordered risky military undertakings. A "madman" president, whether Trump or Pompeo - who is an establishment figure much more than Trump, by the way, will only act in the framework defined by the deep state.
GDP growth only tells part of the story, and even this has meanwhile recovered, as Iran's economy gradually adjusted to the enhanced sanctions environment (such a process takes some time). Iran's progress in defense industries and military power has continued unabated. Development of infrastructures as well.
Thirty years ago, Iran only had two heavyweight strategic allies (Syrian state, Lebanon's Hezbollah party and armed wing). Today, it has four (the previous ones plus the Iraqi PMU and Yemen's Ansarallah and allies). We might add the Palestinian Resistance. Of course the enemy will try everything in its power to disrupt the Resistance Axis. But it's the end result which counts, not intermediate stages or kill ratios.
In Syria, the enemy completely failed in reaching its objectives, which had been clearly announced in the form of the oft repeated slogan "Assad must go". Iran is more entrenched in Syria than it used to be 10 years ago. Whether or not Syria was subjected to war doesn't nullify this fact and it doesn't negatively affect Iran's position in the Levant. On the contrary: it is Iran which is filling the vacuum left by a relatively weaker Syrian central state in key areas, including on the border with occupied Golan.
In Iraq, the so-called civil society movements critical of Iran had been kick started while shahid Soleimani was here. The current Iraqi PM too had been present back then. Shahid Soleimani's martyrdom did not lead to any form Iranian retreat from Iraq.
I mentioned the US regime change policy in this very discussion. See my previous posts. Moreover, I've often comment it elsewhere.
The US has not resorted to the military option because Iran's deterrence power prevented them from doing so. Were it not for Iran's military prowess, incredibly well thought out defensive doctrine and astute policy making, Washington would have launched military operations against Iran. That's where raising the cost of military action comes into play as a key factor of deterrence.
But Iraq was? Afghanistan was? Libya as well?
Iran doesn't need to do anything of the sort. She only needs to survive and keep progressing. That alone would defeat openly declared US strategic goals and imply victory for Islamic Iran.
The goal matters. Only the goal. And it is nowher in reach for Washington, even through these means. Naturally, they will cause some disturbances. But these are irrelevant as long as they don't bring about a downfall of the Islamic Republic.
US sanctions have not prevented Iran from developing. They've been, in many respects, a blessing in disguise even, forcing Iran to invest in the expansion of domestic production and technology, and to steer the economy towards self-sufficiency as much as possible.
Iran doesn't aim to dominate. Domination in geopolitics is an imperial concept. Iran seeks to empower liberation and resistance movements and governments. And has never been as successful in this regard.
As said: the US regime and the globalist oligarchy have no tolerance for independent states. They vassalizes its own allies. A state that not only manages to successfully preserve its sovereignty but what is more, is steadily challenging imperial interests and thus setting a potential example to follow for others, is even more of a thorn in their side.
It is what Iran meant when she said that there will be no negotiations with the killers of shahid Soleimani. Iran held her promise.
Now, as to whether or not it is a sound idea to negotiate with the EU after Biden replaced Trump, I can only reference user Mohsen's post once again, which I quoted previously. Another great assessment was offered by user sanel1412 here:
https://defence.pk/pdf/threads/iranian-chill-thread.283137/post-13553638
This time around, it is Iran which has the upper hand.
Since shahid Soleimani's martyrdom was brought up as an argument for an alleged lack of deterrence on Iran's part, let's put it this way: the cowardly strike against shahid Soleimani didn't cause any strategic setback for Iran in either of the dossiers of concern for the US regime: be it the nuclear program which provides Iran with a potential breakout capability, or Iran's ballistic missiles, Iran's regional presence and so on.