To be honest, as far as I'm aware Luther was not all that influenced by Savonarola. Apparently Luther had read, and in fact wrote a preface for and re-published Savonarola's Prison Meditations on Psalms 31 and 51, and there are a lot of references to a quote from Luther commending Savonarola's doctrine on justification, but I'm having trouble tracking down the original quote - none of the mentions of it I can find so far give an original citation; it's either uncited, or cited from other secondary sources I don't have immediate access to. I found the quote in an old 1948 journal article, but sadly it doesn't give the citation from Luther's works to help me find more (I know, I'm a Luddite without access to all of Luther's works on Logos...):

Though the feet of this holy man are still soiled by theological mud, he nevertheless upheld justification by faith only without works, and therefore he was burned by the Pope.

My impression is that Luther may have later recognized some similarities between himself and Savonarola, but the latter's works didn't play a huge role in shaping Luther's own thought. Looking at Savonarola's life and thought, I do find it hard to believe that Luther was significantly impacted by him, and his allusion to the "theological mud" underscores the disagreement Luther saw on other points.

Now, Jan Hus is another matter entirely. This goes back to the Leipzig debate with Eck in 1519, where Eck flat-out accuses Luther of being a Hussite heretic. Luther initially resisted at first (understandably his first impulse was to deny being a heretic, and Hus had been condemned at a church council), but he then looked more into Hus' writing and came to the conclusion that, well, old Jan hadn't been so far off base after all. He was forced by Eck to publicly admit at Leipzig that he was in some agreement with Hus - so perhaps Luther independently arrived at similar conclusions before 1519, but after that he was conscious of Hus as a predecessor of some sort. To what degree he was actively influenced or guided by Hus' thought is something I don't feel able to answer right now, but perhaps someone has already done work on that; if not, it'd make a great dissertation for somebody.

As for Wycliffe, we can say that Luther was at least indirectly influenced by him - Wycliffe influenced Hus, and Luther was well aware of Hus. He also seems to have been aware of Wycliffe in some capacity, but again I haven't located any definitive indication that he read Wycliffe first-hand or was significantly influenced.

You might be interested in an earlier answer of mine, Could people in 1510 suspect that something big was about to happen? (Um, it was one of my first--I think it might have been part of my flair app, even--so as they say, lower your expectations). It doesn't focus so much on Luther as theologian, but more on general religious currents of the time.

The Reformation is interesting as an event in historical memory because it's one area where a lot of the Western public has a decent idea of the outline--at least enough to laugh at Reformation Day memes--and yet scholars often have a very different understanding behind the same facts/events. One of the biggest distinctions, I think, is that historians of the past fifty or so years have tended to emohasize the Ref as an outgrowth of late medieval religion, as much intensification and continuation as rejection. (After all--a large percentage of Europe stays Catholic!) Like, the three medieval reformers raised in this thread are Hus, Wyclif, and Savonarola--all of whom were implicated in heresy, two of whom died at the stake. Reformation scholars would be quicker to point to Jean Gerson, Johann von Stauptiz, even humanist biblical scholarship as immediate and direct influences (and with Gerson in particular, we are talking the orthodox of orthodoxy; he is one of the most important Church figures of the 15th century on nearly every level). I'm going to crib a famous example from the wonderful scholar Berndt Hamm, albeit while stressing this is one example of particular importance to Luther; I do not think it was the turning point of lay people being attracted to evangelical teaching. (Mostly because when lay people write about evangelical reform in the 1520s, it's not anywhere near the most common theme.) But I digress.

The famous line about Luther's conversion to evangelical reform, which would become Reformation when he could not convince the Church hierarchy of his views, is that the intense, overbearing requirements of confession and penance caused immense anxiety--people believed they had to work for their salvation. Luther portrays himself as absolutely frantic over this, devastated that he could never be "good enough" to earn salvation through his good works, desperate to make himself that good. He found freedom in the realization from Scripture, according to his interpretation of it, that works don't matter. Humans have absolutely no power or control over our salvation. God ordains everything, has already ordained everything. (This frees the Christian to follow God's commandments joyfully, rather than either keeping them out of anxiety or failing to keep them because they believe there's no possible way to be "enough.") That seems like a pretty big gap: earn your way to heaven (since Christ's death has made the ticket available; medieval theology of salvation of course requires the sacrifice on the cross) versus God pays the whole ticket.

Hamm was one of the first scholars to take fifteenth century and early 16C pastoral theologians seriously, rather than rejecting them as the failures that created Luther. He studied especially preachers that came out of Luther's own religious formation, the Augustinian order. What he found are actually a variety of internediary perspectives! One step removed from "these works are required" is the teaching that the desire to do good is enough. ("Good works" being a combination of being a good person but more following Church teaching, completing the confessional triad of contrition, confession, receiving absolution and a penance to do, and clean-souled reception of the Eucharist). The idea resonates in what I said above about Luther's anxiety that he could never do enough/do it well enough. Clearly he wanted to, right?

Well, modern people who know how anxiety works can probably see the next step coming. Other sermons stress that the desire to desire to be good is enough. That's right, there's an even more basic option for people who worry not just about whether their actions are good enough but whether they even want salvation "enough". The bar gets lower and lower. Honestly, what I always think of is the emotions machine (uh...mood organ? Does that sound right?) in Do Androids Dream of Electric Sheep. You can dial actual feelings, but also something like "the desire to watch TV even if nothing good is on" (might be "no matter what is on;" I haven't read the book in a decade). But, as we find out during a fight between Deckard and his less tuned in wife, what if you don't want to dial anything at all? There is a setting to make you want to dial.

I bring up this example for one more reason. Hamm's research situated Luther's pastoral teaching on faith and works "in the context of late medieval piety", as Bast translates it. There is a progression from works to the desire to do works to thhe desire to desire to do works to God supplies the desire. But while it is a progression on ine hand, there is at the same time a gulf between humans incubating the desire and God impressing it. (d.h. Free will versus the bondage of the will).

Make no mistake. The Reformation absolutely was "a medieval event"--and not just medieval heresy. But Reformation theology and praxis introduce some radically new things to Christianity in the 16th century, even if the Reformers insisted their faith was not innovation but restoration.

Follow-up: Was Luther at all influenced by John Wycliffe and/or Jan Hus?