That event happened before the book of Matthew was completed, for obvious reasons. That event happened while Matthew was alive, and he was still on earth after that, to tell the story.
That resurrection is not mentioned in any Epistle. Therefore, you can assume that they are not related to the salvation of the church, and by implication, their resurrection into eternal life. Nothing in the Epistles is connected to a past saints resurrection into eternal life.
Some say they were the saints of the old testament, which it is kind of a stretch, and very hard to give solid arguments for it. I heard of somebody connecting it to Ez 37:12-14, and then to
Acts 2:38. Maybe. The most plausible theory is that they were just godly people resurrected as Lazarus was.
Brother, just to warn you, this forum could confuse you tremendously. I highly recommend that, if you haven't done it before, you study carefully hermeneutics and some rhetoric as well, in order to evaluate what they say in this forum. Also, remember this are not formal debates, so the person that it is actually right regarding what it is the actual truth, may not be spending a significant amount of time to engage fully with errors here and express their arguments thoroughly.