Show how much you know about the Bible, very little. Paul wrote those based on the salutation he wrote at the end of his writings. The general theme goes is along the lines of "The grace of the Lord Jesus Christ be with you always." It is not always that exact phrase but the wording and meaning is similar. This is how we can know Paul wrote Hebrews and also by the style of the book. Plus the fact that each of them specifically states that Paul is the author and the author of all the pastorals knew both Timothy and Titus, whom Paul knew.
There's no need to be offensive. I know just as much as you do about the content of the Pastorals and Paul's writing style, but my interpretation differs from yours. The mere fact that a text contains in it a claim to be written by Paul does not, in itself, mean that it was.
For example, consider this series of texts, in which Paul and Seneca exchange letters. These also contain salutations by Paul. But you surely don't think that these are genuine. Paul and Seneca didn't really write to each other - someone just forged a bunch of letters to make it seem like they did. So unless you think that Paul really wrote to Seneca, you must admit that just because a text appears to be a letter by Paul, that doesn't mean it really is.
Moreover, 2 Thessalonians 2:2 specifically states that there were letters circulating "as if from" Paul, so we know that such texts existed (indeed 2 Thess itself may well be one of them). There is on the face of it no reason, therefore, why the Pastoral epistles or indeed any other Pauline text should not be among these pseudonymous writings. Each one must be evaluated according to the evidence. The mere fact that a text says "lots of love from Paul" at the end isn't good enough evidence, since that's exactly what a pseudonymous text would say too.
In the case of the Pastorals, New Testament scholars are nearly unanimous in thinking them inauthentic. This is on the basis of the language (they are written in a very different style from Paul's authentic letters), the theology (again, it is quite different), and the church situation they seem to presuppose (it is far more structured than the much more informal situation envisaged in texts such as 1 Corinthians). Plus, if the Pastorals are authentic, then Paul survived his imprisonment in Rome and travelled to Spain as he planned, but there is no other evidence that this happened, which is not what you'd expect (where are all the letters to the Spanish churches, descriptions of his travels in Acts or other texts, etc.?).
You may think that this evidence is inconclusive, but don't label those who disagree with you as ignorant. That is neither very charitable nor sensible.
I'm puzzled that you think the book of Hebrews is written in the same style as Paul's letters. It isn't. Indeed it isn't really a letter at all, but a treatise, written in a rhetorical Greek style with a well structured overall argument. This is quite different from Paul's letters, which are occasional writings (i.e. responding to specific issues) without overall structure of this kind, and where the arguments are short and to the point. They also follow the conventional structure of classical letters, although they distort it, whereas Hebrews doesn't. As I said, it's not really a letter at all. There's good reason to think that Paul's letters proved so popular in the early church that people came instinctively to think that any Christian writing ought to be in letter form, which is why Hebrews imitates this form in a very slight way. But no way is it by Paul. If it were, it would say so. Paul was not a modest man.