Many people forget that he did get Russia involved in two major wars, I am not sure about the no obvious reason with the Japanese Russian War, I will agree with WW1
War with Japan was a complete idiocy caused by a number of very questionable decisions, some of which had been made by the unquestionably intelligent people (like Witte) who looked at the situation from a completely wrong perspective. As an absolute monarch Nicholas had an ultimate responsibility for what happened.
1. "Everybody" (including Witte who considered the whole situation strictly from a financial perspective) considered war with Japan a complete impossibility for the next few decades. As a result, instead of putting all possible effort into finishing the Trans Siberian Railroad, the investments had been made into the railroads in China and Korea because they were bringing immediate income. IIRC, the main line of the trans Siberian Railroad was finished only in 1905 and additional works continued until 1916 (Amur River Bridge at Khabarovsk).
2. The money had been loaned to the Chinese government to pay reparations to Japan (IIRC, something on the scale of 150M rubles but don't quote me on this

). So you can say that to a great degree Russia paid for Japanese rearmament.
3. Infatuation with an idea of having a warm water port resulted in Port-Arthur/Dalnii adventure which cost huge amounts of money and required railroad construction outside Russian territory. Now, look at the map below.
Entry into the internal harbor is very narrow making getting in and out quite difficult and allowing to block it by sinking one or two ships (and a big part of it was dry during the low tide leaving a limited space for the ships, look at the grey line inside the harbor). Small wonder that at the time of Japanese attack most of the Russian squadron was in an outer harbor, vulnerable to an attack. Due to the limited amounts of money allocated for the fortification works (15M rubles altogether) these works should be finished only by 1909. Only 4.5M had been spent by 1904, mostly on the sea-side fortifications. When the war started the land-side construction was going with all possible speed but it was impossible to finish 5 years job in 5 months.
4. Russian Pacific fleet had been split between Port Arthur and Vladivostok, none of which had adequate facilities for the major repairs. The money spent on Port-Arthur and Dalny could be used to address this issue. Besides, the whole fleet located in Vladivostok would be both safer and stronger.
5. The military refused to allow usage of Port Arthur as a commercial port so the extra resources had been spent to built such a port in Dalny, on a far end of the East-China Railroad. The project cost 30M rubles and the only beneficiary were Japanese who captured it easily and used as a military-naval base (with all Russian-built port installations, depots, repair facilities, etc.): as a commercial port it could not compete with the Chinese
Yíngkǒu.
6. A prerequisite of the whole plan was Russian dominance on the land, which did not happen in OTL making fall of Port Arthur just a matter of time.
7. The whole thingy with Port Arthur was a clear spit into the Japanese face just waiting for the trouble to happen.